Back support structure

ABSTRACT

A tiltable chair including a housing, a back support pivotally attached to the housing about a first horizontal axis and a seat support pivotally attached to the back support about a second horizontal axis and moveably supported by a curved track formed on the housing. A leaf spring includes a first end supported by the housing and a second end biasing the back support and seat support in an upward direction. Preferably, a fulcrum member, which includes a support surface having a curvilinear contour, is moveably supported in the housing and engages a bottom surface of the spring intermediate the first and second ends of the spring. Preferably, a linkage mechanism including a first and second link is adapted to adjust the position of the fulcrum. In another preferred embodiment, a gear housing is removably disposed in said housing and coupled to the fulcrum. In one preferred embodiment, rearward and forward tilt limiters are provided. In various preferred embodiments, the chair further includes a backrest having a plurality of openings, and armrests that are vertically, laterally and pivotally adjustable. In a preferred embodiment, a kit for assembling a seating structure includes a tilt housing having a plurality of connector arrangements comprising at least a first and second connector arrangement, a first seating arrangement having a first mounting arrangement configured to be connected to the first connector arrangement, and a second seating arrangement having a second mounting arrangement configured to be connected to the second connector arrangement.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/418,578, filed Oct. 15, 2002 and U.S. ProvisionalApplication No. 60/356,478, filed Feb. 13, 2002, the entire disclosuresof which are hereby incorporated herein by reference.

BACKGROUND

[0002] The present invention relates generally to tiltable chairs, andin particular, to a tilt chair having a flexible back, adjustablearmrests, and an adjustable seat depth, and methods for using and/oradjusting the chair, including one or more of the seat, backrest andarmrests.

[0003] Chairs of the type typically used in offices and the like areusually configured to allow tilting of the seat and backrest as a unit,or to permit tilting of the backrest relative to the seat. In chairshaving a backrest pivotally attached to a seat in a conventional manner,the movement of the backrest relative to the seat can create shearforces which act on the legs and back of the user, and which can alsocreate an uncomfortable pulling of the user's shirt, commonly called“shirt-pull.”

[0004] To enhance the user's comfort and to promote ergonomicallyhealthy seating, synchro-tilt chairs provide for the seat and backrestto tilt simultaneously, but at different rates, preferably with the backtilting at a greater rate than the seat. In general, synchro-tilt chairsare usually configured as a four-bar linkage or as a three-bar, slidelinkage. In a three-bar, slide configuration, the sliding path istypically linear. Such chairs often have a multiplicity of componentsand parts that can be difficult and time consuming to assemble and whichrequire multiple fasteners or joints to connect the components.

[0005] In addition, synchro-tilt chairs normally employ compressionand/or tension springs, torsion springs and/or torsion bars, or leafsprings to bias the seat and back upwardly and to counterbalance therearward tilting of the user. Chairs using these types of springs canhave various limitations associated with the type of spring used thereinas explained in U.S. Pat. No. 6,250,715, entitled Chair, and assigned toHerman Miller, Inc., the entire disclosure of which is herebyincorporated herein by reference. In addition, the mechanisms used toadjust the load on the spring(s), or the load capability of thespring(s), typically are complicated, and/or require multiple, excessiverotations of a knob or other grippable member to obtain the desiredsetting.

[0006] It is also desirable to provide a chair that can be adjusted toaccommodate the various needs and sizes of the user. For example, it isoften desirable to provide a chair having adjustable armrests and anadjustable seat depth. For example, armrests can be provided withvertical adjustment capabilities, lateral adjustment capabilities andpivotable adjustment capabilities about a vertical axis. Often, however,armrests fail to provide such capabilities in combination, and/or employcomplex, moving parts and assemblies that can be expensive tomanufacture and assemble and difficult to use. Moreover, armrests havingvertical adjustment capabilities often employ a support member thatextends vertically down along the side of the chair, where the armrestor support member can interfere with the user's legs and other objectsas the user moves about in the chair. In addition, the range ofadjustment is typically limited to the length of the support member.However, the longer the support member, or the further it extends belowthe seating surface, the more likely it is to increase the foot print ofthe chair and interfere with the mobility of the chair.

[0007] Chairs with adjustable seat depths often employ devices andmechanisms to shift the entire seat in a forward and rearward directionrelative to the backrest. Therefore, such chairs must provide forstructure to allow the seat to move relative to the backrest while atthe same time bearing the load of the seat and user. Moreover, suchchairs typically must employ an extra support member which allows theseat to move thereon, for example, when the seat or support member areintegrated into the linkage assembly.

[0008] Typically, backrests having a resilient and/or flexible material,whether a fabric, elastic membrane or plastic mat, are often supportedby a peripheral frame, which surrounds the material. Such construction,however, does not ordinarily permit flexing of the material at theperiphery of the backrest, or allow for torsional movement of thebackrest. In addition, even in those chairs that employ a resilientmaterial, the material often has uniform mechanical and physicalproperties across the entire portion of the material.

[0009] Finally, as disclosed for example in U.S. Pat. No. 5,873,634 toHeidmann et al., it is known to connect different seating arrangementsto a control housing. However, Heidmann discloses connecting differentseating arrangements to a tilt control housing and back support atcommon connection points. Accordingly, the overall kinematics of thechair cannot be altered or varied, but rather are predetermined by thecommon connection points. In such a device, only localized adjustmentswithin each seating arrangement can be varied between the differentseating arrangements.

SUMMARY

[0010] The present inventions are defined by the claims, and nothing inthis section should be read as a limitation on those claims. Rather, byway of general introduction and briefly stated, various preferredembodiments are described that relate to a tiltable chair having aflexible back, adjustable armrests, an adjustable seat depth, variouscontrol mechanisms and linkage assemblies, and methods for the use ofthe various preferred aspects.

[0011] For example and without limitation, in one aspect, the preferredembodiments relate to an adjustable armrest, and the method for the usethereof. In one preferred embodiment, an armrest assembly for a seatingstructure includes a support member comprising an upwardly extendingcurved spine portion having a first defined curvature and a stemslidably disposed on the support member and comprising a curved portionhaving a second defined curvature corresponding to and mating with thefirst curvature of the spine portion. An armrest is preferably supportedby the stem. A latch mechanism is moveable between at least an engagedposition and a disengaged position, wherein the latch mechanism engagesat least one of the stem and the support member to prevent movementtherebetween when in the engaged position. The stem is moveable relativeto the support member when the latch mechanism is in the disengagedposition.

[0012] In another aspect, one preferred embodiment of the armrestassembly includes a support member, a stem slidably disposed on thesupport member, an armrest supported by the stem, a latch mechanism andan index member. The latch mechanism is moveable between at least anengaged position and a disengaged position. The latch mechanism engagesat least one of the stem and the support member to prevent movementtherebetween when in the engaged position. The stem is moveable relativeto the support member when the latch mechanism is in the disengagedposition. The index member selectively engages at least one of thesupport member and the stem when the latch mechanism is in thedisengaged position as the stem is moved relative to the support member.

[0013] In yet another aspect, in one preferred embodiment, an armrestassembly comprises a platform and an armrest support moveably supportedon the platform. The armrest support is moveable between at least afirst position and a second position. A linear gear is disposed on oneof the platform and the armrest support and extends in a substantiallyhorizontal direction. A pinion gear is rotatably mounted on the other ofthe platform and the armrest support about a substantially verticalrotation axis. The pinion gear meshes with the linear gear as thearmrest support is moved relative to the platform between at least thefirst and second positions.

[0014] In one preferred embodiment, the armrest assembly includes a pairof pinion gears meshing with each other and a pair of linear gears. Alsoin one preferred embodiment, one of the platform and the armrest supportincludes a guide member that moves in a track formed in the otherthereof as the armrest support is moved relative to the platform. In onepreferred embodiment, first and second guide members move in first andsecond tracks.

[0015] Various methods of using the various preferred embodiments of thearmrest assemblies are also provided.

[0016] In another aspect, one preferred embodiment of a seatingstructure includes a primary seat support having a rear portion and afront portion and an auxiliary seat support having a rear portion and afront portion. The rear portion of the auxiliary seat support isconnected to the front portion of the primary seat support. At least aportion of the auxiliary seat support is flexible, wherein the frontportion of the auxiliary seat support is moveable between at least afirst and second position relative to the rear portion of the auxiliaryseat support as the flexible portion of the auxiliary seat support isflexed.

[0017] In one preferred embodiment, the seating structure includes alinkage assembly connecting the front portion of the auxiliary seatsupport and one of a housing, which supports the primary seat support,and the primary seat support. In one preferred embodiment, the linkageassembly includes first and second links.

[0018] In one preferred embodiment, the seating structure furtherincludes a lock device releasably connected between the auxiliary seatsupport and one of the housing and primary seat support.

[0019] In one preferred embodiment, the seating structure comprises aseat support comprising a forward portion, a rear portion and opposite,laterally spaced sides. At least the forward portion is bendable about asubstantially horizontal and laterally extending axis between at least afirst and second position, wherein the forward portion has a greatercurvature when in the second position compared with the first position.A lock device is moveable between at least an engaged position and adisengaged position, wherein the lock device maintains the seat supportin at least one of the first and second positions when in the engagedposition, and wherein the seat support is bendable between at least thefirst and second positions when the lock device is in the disengagedposition.

[0020] Various methods for adjusting the depth of the seat, or thecurvature of the front portion thereof, are also provided.

[0021] In another aspect, one preferred embodiment of a backrest for aseat structure comprises a frame member and a compliant, resilient backmember having a top, a bottom and opposite sides. The back member ismounted to the frame member. The back member includes a lumbar region, athoracic region disposed above the lumbar region, and a lower regiondisposed below the lumbar region. The lumbar region comprises a firstarray of openings formed therethrough, with the first array comprising afirst plurality of staggered, elongated openings that are elongated in adirection from the top to the bottom of the back member. The thoracicregion comprises a second array of openings formed therethrough, withthe second array comprising a second plurality of staggered, elongatedopenings, which are elongated in a direction from the top to the bottomof the back member. The first plurality of openings has a greaterelongation on average than the second plurality of openings.

[0022] In another preferred embodiment, a backrest for a seat structureincludes a frame member comprising an upper support member and a lowersupport member spaced from the upper support member, with the uppersupport member having opposite shoulder portions. A fabric member havinga front, body-supporting surface and a rear surface comprises at leastone pocket that is received on the opposite shoulder portions. Thefabric member is connected to the lower support member and extends intension between the upper and lower support members. The fabric membercomprises a central thoracic region that is free of contact on the rearsurface thereof. In another aspect, one preferred embodiment of a chaircomprises a housing comprising a track having a curvilinear supportsurface formed within a vertical plane. A back support is pivotallyconnected to the housing about a first horizontal axis, and a seatsupport is pivotally connected to the back support about a secondhorizontal axis and is moveably supported on the support surface of thetrack.

[0023] In yet another aspect, the chair comprises a housing, a seatsupport supported by the housing, and at least one leaf springcomprising a first end supported by the housing and a second end biasingthe seat support in an upward direction, wherein the at least one leafspring flexes within a substantially vertical first plane. A fulcrummember is moveably supported by the housing and has a support surfaceengaging the at least one leaf spring between the first and second ends.The support surface is preferably not symmetrical about any laterallyextending second vertical plane oriented substantially perpendicular tothe first plane.

[0024] In yet another aspect, one preferred embodiment of a chairincludes a fulcrum member having a curvilinear support surface engagingat least one leaf spring between a first and second end. Preferably, atangent of any point along the support surface of the fulcrum slopesrearwardly and downwardly.

[0025] In yet another aspect, one preferred embodiment of a seatingstructure includes a linkage assembly comprising a first and second linkpivotally connected to a housing about a first pivot axis. The firstlink is pivotally and slidably connected to a fulcrum at a second pivotaxis spaced from the first pivot axis and the second link is pivotallyand slidably connected to the fulcrum at a third pivot axis spaced fromthe first and second pivot axes. In one preferred embodiment, anactuator member pivotally engages the first and second links at pivotaxes spaced from the first, second and third pivot axes. In variouspreferred embodiments, various tracks are formed in one of the links andthe fulcrum member, the actuator member and various brackets. Guidemembers are formed on the other of the links and the fulcrum member, theactuator member and various brackets. In one preferred embodiment,certain of the tracks, preferably formed in the brackets, are curved.

[0026] In yet another aspect, one preferred embodiment of a seatingstructure includes a housing and a support member pivotally mounted tothe housing. A tilt limiter member is moveably mounted to one of thehousing and the support member, and a stop member is connected to theother of the support member and the housing. An actuator mechanism iscoupled to one of the housing and the support member and includes aspring having a first and second arm, a drive link and a follower link.The drive link is pivotally mounted to one of the housing and thesupport member about a first axis and engages the first arm of thespring at a first location spaced from the first axis. The follower linkis pivotally mounted to one of the housing and the support member abouta second axis spaced from the first axis and engages the second arm ofthe spring at a second location spaced from the second axis. Thefollower link is pivotally coupled to the tilt limiter member.

[0027] In one preferred embodiment, the stop member has a downwardlyfacing stop surface and the tilt limiter has an upwardly facing bearingsurface engaging the stop surface. In an alternative preferredembodiment, the stop member has at least one upwardly facing stopsurface and the tilt limiter has a downwardly facing bearing surfaceengaging the at least one stop surface. In yet another preferredembodiment, the tilt limiter member comprises a first and second tiltlimiter member moveably mounted to one of the housing and the supportmember, and the stop member comprises a first and second stop memberconnected to the other of the support member and the housing. Theactuator mechanism comprises first and second springs each having afirst and second arm, spaced apart first and second drive links eachpivotally mounted to one of the housing and the support member about thefirst axis, and first and second follower links.

[0028] In another aspect, in one preferred embodiment, a kit forassembling a seating structure includes a tilt housing having aplurality of connector arrangements comprising at least a first andsecond connector arrangement, a first seating arrangement having a firstmounting arrangement configured to be connected to the first connectorarrangement, and a second seating arrangement having a second mountingarrangement configured to be connected to the second connectorarrangement. In another aspect, a method of assembling a seatingstructure includes providing a tilt housing having a plurality ofconnector arrangements comprising at least a first and second connectorarrangement, selecting one of a first and second seating arrangements,wherein the first seating arrangement includes a first mountingarrangement configured to be connected to the first connectorarrangement, and wherein the second seating arrangement includes asecond mounting arrangement configured to be connected to the secondconnector arrangement, and connecting the selected one of the first andsecond seating arrangements to the tilt housing.

[0029] In yet another aspect, the seating structure includes a tilthousing, a seating structure pivotally connected to the tilt housing anda biasing member applying a biasing force to the seating structure asthe seating structure is pivoted relative to the tilt housing. Anadjustment mechanism is operably connected to the biasing member and isoperable to adjust the biasing force applied by the biasing member. Theadjustment mechanism includes a gear housing removably disposed in thetilt housing. The gear housing is rotatably connected to the tilthousing about an axis. The gear housing includes first and secondlocator portions abutting the tilt housing. The first locator portionprevents the gear housing from moving relative to the tilt housing in afirst direction. The second locator portion prevents the gear housingfrom rotating relative to the tilt housing about the axis.

[0030] In another aspect, a support member for a seating structurecomponent includes a first support member having a first plurality ofspaced apart fins and a second support member having a second pluralityof spaced apart fins. The first support member is secured to the secondsupport member with the first plurality of fins nested between thesecond plurality of fins. In one preferred embodiment, a back member isconnected to at least one of the first and second support members.

[0031] In yet another aspect, a control device for an adjustable seatingstructure includes a first adjustment control positioned in anorientation approximating a seating member. The first adjustment controlis moveable about a horizontal axis. A second adjustment control ispositioned adjacent the first adjustment control in an orientationapproximating a backrest member. The second adjustment control ismoveable about the horizontal axis. The first adjustment control and thesecond adjustment control, in combination, generally resemble a seatingstructure. In one preferred embodiment, the first adjustment control andthe second adjustment control are coupled to a forward tilt limiter anda rear tilt limiter respectively.

[0032] Various methods of assembling a tilt chair, and of using andadjusting a tilt chair having an adjustable fulcrum member and varioustilt limiters also are provided. For example, various preferredembodiments of the seating structure include inserting an insert memberinto a pivot tube to deform or expand the tube so as to fixedly securethe tube to a wall or other structure. In addition, other preferredembodiments include inserting a pivot member having a key surfacethrough a mouth of a bearing member and rotating the pivot member so asto locate the pivot member in the bearing member. In yet anotherpreferred embodiment, a plurality of tilt housing components aredisposed on an annular bushing and an end of the bushing is deformed tocapture the components on the bushing.

[0033] The various preferred embodiments provide significant advantagesover other tilt chairs and seating structures, including chairs andseating structures having adjustable armrests, backrests, seats and tiltcontrols. For example, in one preferred embodiment, an improved tiltcontrol mechanism is provided. The resistive force of the leaf springsis easily and simply adjusted by moving the fulcrum memberlongitudinally within the housing. In one embodiment, a removable gearhousing can be quickly easily installed without fasteners and the likefor adjusting the fulcrum member. In another preferred embodiment, theconfiguration of the linkage assembly allows the user to quickly movethe fulcrum over a wide range of longitudinal positions with minimalturns of the drive shaft. In addition, the unique shape of the supportsurface on the fulcrum provides a variable balancing spring rate, whichresults from an increasing amount of contact between the support surfaceand the spring as the user tilts rearwardly.

[0034] The three bar slide mechanism also provides several advantages.For example, the linkage provides for a synchrotilt chair wherein theback tilts at a greater rate than the seat, but avoids the use of afourth bar, which can add to the complexity and manufacturing costs ofthe chair. Indeed, the overall design is greatly simplified by forming“bars” out of the housing, seat support and back support. Additionally,the use of a slide member allows for the assembly to be made in a morecompact and aesthetically pleasing form.

[0035] The modular tilt housing also provides significant advantages. Inparticular, different seating arrangements can be mounted or connectedto a single tilt housing with different connection configurations,thereby providing seating structures with different kinematics andappearances. At the same time, a single modular tilt housing providessignificant savings and reductions in inventories. Indeed, completelydifferent chairs operating on completely different kinematic principlescan be assembled from a single tilt housing. The modular tilt housingcan also be configured to support different actuation mechanisms atvarious mounting locations. The back support can also be configured as amodular member, wherein it is adapted to support and be coupled withdifferent seat configurations at different connector locations, therebyproviding additional flexibility in assembling different seatingstructures with different kinematics and appearances.

[0036] The preferred embodiments of the armrests also provideadvantages. For example, the curved spine and stem provide maximumvertical adjustment, while maintaining a relatively open area beneaththe seat. In addition, the height of the armrests can be adjustedquickly and easily, with the indexing member providing an audible signalto the user about the various available positions. Moreover the armrestscan be laterally and pivotally adjusted quickly and easily, while themechanism, with the interaction of gears, maintains a firm, robust feelto the user.

[0037] The preferred embodiments of the adjustable seat also provideadvantages. For example, the depth of the seat can be adjusted withouthaving to move the entire seat, or in other words, while maintaining arear portion of the seat in the same position. Such construction avoidsthe need for additional support members. In addition, the adjustmentmechanism can be easily grasped and manipulated the user to adjust thedepth of the seat. Moreover the front portion of the seat, when bentdownwardly, provides transitional support for the user's legs whensitting down or standing up from the chair.

[0038] The preferred embodiments of the tilt limiter controls alsoprovide advantages. For example, in one embodiment, both of the forwardand rearward tilt limiters are spring loaded, such that the position ofeach can be adjusted at any time, but with the limiter being moved onlywhen the load is relieved from the chair. In another embodiment, therear tilt limiter is supported by the tilt housing, which carries theload applied by the back support against the tilt limiter, whichincreases the overall robustness of the limiter without having tounnecessarily fortify the pivot connections of the tilt limiter.Moreover, an indexing feature provides the user with a distinctindication that an available setting has been achieved.

[0039] In addition, the orientation and/or shape of the adjustmentcontrols provides indicia to the user about the functionality of thedevice or mechanism coupled to the control. For example, a first andsecond adjustment control can be oriented to generally resemble aseating structure, with each of the adjust controls being coupled todevice or mechanism that controls the adjustment of the correspondingseating structure member, for example the seat or backrest.

[0040] The support member for a seating structure component having afirst support member with a first plurality of spaced apart fins and asecond support member with a second plurality of spaced apart fins alsoprovides significant advantages. In particular, the first and secondsupport members in combination provide substantial bending strength, yetprovide torsional flexibility by way of the fins moving relative to eachother. In this way, the support member, when used for example as abackrest spine, provides resistance to bending, but allows the backrestto flex torsionally about a longitudinal axis. In addition, the firstand second support members can be configured to provide for the couplingof various back members and adjustment devices. For example, the firstand second support members can be configured to define a gaptherebetween to allow for an engagement member to be insertedtherethrough wherein it can engage one of the first and second supportmembers. In addition, the support members can be easily and cheaplymanufactured by various molding processes.

[0041] The present invention, together with further objects andadvantages, will be best understood by reference to the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a perspective view of an armrest assembly.

[0043]FIG. 2 is an exploded perspective view of one embodiment of anarmrest assembly.

[0044]FIG. 3 is an enlarged partial cross-sectional view of a lever andindex member engaging a rack.

[0045]FIG. 4 is an enlarged partial side view of the lever and indexmember of FIG. 3 engaging a rack.

[0046]FIG. 5 is a perspective view of an index member.

[0047]FIG. 6 is an exploded top perspective view of one embodiment of anupper portion of armrest assembly.

[0048]FIG. 7 is a bottom view of one embodiment of an armrest support.

[0049]FIG. 8 is an exploded bottom perspective view one embodiment of aportion of an upper portion of an armrest assembly.

[0050]FIG. 9 is an enlarged partial top perspective view of oneembodiment of a portion of an upper portion of an armrest assembly.

[0051]FIG. 10 is an enlarged partial top perspective view of anotherembodiment of a portion of an upper portion of an armrest assembly.

[0052]FIG. 11 is a perspective view of one preferred embodiment of achair.

[0053]FIG. 12 is a front view of the chair shown in FIG. 11.

[0054]FIG. 13 is a right side view of the chair shown in FIG. 11, withthe left side view being a mirror image thereof.

[0055]FIG. 14 is a top view of the chair shown in FIG. 11.

[0056]FIG. 15 is a partial enlarged front view of the seat connected tothe armrest.

[0057]FIG. 16 is a cross-sectional view of the armrest and seat takenalong line 16-16 of FIG. 15.

[0058]FIG. 17 is a top perspective view of one embodiment of a seatsupport assembly.

[0059]FIG. 18 is a bottom perspective view of the seat support assemblyshown in FIG. 17.

[0060]FIG. 19 is an exploded bottom perspective view of the seat supportassembly shown in FIG. 17.

[0061]FIG. 20 is an exploded top perspective view of an alternativeembodiment of a seat support assembly.

[0062]FIG. 21 is a cross-sectional view of a portion of a seat supportmember.

[0063]FIG. 22 is a cross-sectional view of a carrier member.

[0064]FIG. 23 is rear perspective view of a backrest.

[0065]FIG. 24 is a front view of a backrest frame member.

[0066]FIG. 25 is a partial section cut and side view of the backrestframe member taken along line 25-25 of FIG. 24.

[0067]FIG. 26 is an enlarged partial rear view of the backrest framemember.

[0068]FIG. 27 is a rear perspective view of a lumbar support.

[0069]FIG. 28 is a front view of a back member.

[0070]FIG. 29 is a cross-sectional view of the back member taken alongline 29-29 of FIG. 28.

[0071]FIG. 30 is a cross-sectional view of the back member taken alongline 30-30 of FIG. 28.

[0072]FIG. 31 is a perspective view of the back member.

[0073]FIG. 32 is a side view of the back member.

[0074]FIG. 33 is a rear perspective view of an alternative embodiment ofa backrest.

[0075]FIG. 34 is a rear view of a back member.

[0076]FIG. 35 is a side view of the back member shown in FIG. 34.

[0077]FIG. 36 is an alternative embodiment of a backrest frame member.

[0078]FIG. 37 is a side view of the backrest frame member shown in FIG.36.

[0079]FIG. 38 is a top view of the backrest frame member shown in FIG.36.

[0080]FIG. 39 is a partial cross-sectional view taken along line 39-39in FIG. 23.

[0081]FIG. 40 is a partial cross-sectional view of the back supportconnected to the tilt control housing.

[0082]FIG. 41 is a partial cross-sectional view of the seat supported bythe tilt control housing track.

[0083]FIG. 42 is a partial cross-sectional view of a support column inan elevated and compressed position.

[0084]FIG. 43 is an exploded perspective view of the tilt assembly.

[0085]FIG. 44 is a top view of a fulcrum member.

[0086]FIG. 45 is a side view of the fulcrum member.

[0087]FIG. 46 is an alternative exploded view of the tilt assembly.

[0088]FIG. 47 is another alternative exploded view of the tilt assembly.

[0089]FIG. 48 is a perspective view of the actuator mechanism andlinkage assembly for the fulcrum member.

[0090]FIG. 49 is an exploded view of the linkage assembly for thefulcrum member.

[0091]FIG. 50 is cross-sectional view of the linkage assembly for thefulcrum member.

[0092]FIG. 51 is an exploded view of the tilt control housing and stopmembers.

[0093]FIG. 52 is an exploded perspective view of a tilt limitermechanism.

[0094]FIG. 53 is a perspective view of the back support and tilt limiterassembly.

[0095]FIG. 54 is an exploded perspective view of the back support andtilt limiter assembly.

[0096]FIG. 55 is a partial cross-sectional view of the back supportsecured in a forward tilt position.

[0097]FIG. 56 is a partial cross-sectional view of the back supportsecured in an at-rest neutral position.

[0098]FIG. 57 is a partial cross-sectional view of a portion of the tiltlimiter mechanism.

[0099]FIG. 58 is a perspective view of one embodiment of a tilt assemblyand back support with the springs in a disengaged position.

[0100]FIG. 59 is a side view of one embodiment of a tilt assembly andback support with the springs in a disengaged position.

[0101]FIG. 60 is an exploded perspective view of on embodiment of a tiltassembly and back support.

[0102]FIG. 61 is a front view of one embodiment of the fulcrum member.

[0103]FIG. 62 is a side view of the fulcrum member shown in FIG. 61.

[0104]FIG. 63 is a side view of a rear tilt limiter.

[0105]FIG. 64 is a partial cross-sectional view of a tilt limiter drivemember.

[0106]FIG. 65 is a perspective view of a forward tilt limiter.

[0107]FIG. 66 is a perspective view of an outer tilt housing member.

[0108]FIG. 67 is a perspective view of an inner tilt housing member.

[0109]FIG. 68 is a perspective view of a tilt housing guide member.

[0110]FIG. 69 is an exploded perspective view of an actuation mechanism.

[0111]FIG. 70 is a side view of a gear housing.

[0112]FIG. 71 is a cross-sectional view of one embodiment of theconnection between the seat and armrest.

[0113]FIG. 72 is an exploded perspective view of a lumbar supportassembly.

[0114]FIG. 73 is an exploded perspective view of a backrest assembly.

[0115]FIG. 74 is front view of a back member.

[0116]FIG. 75 is a partial cross-sectional view of a back member takenalong line 75-75 of FIG. 74.

[0117]FIG. 76 is a partial cross-sectional view of a back member takenalong line 76-76 of FIG. 74.

[0118]FIG. 77 is a partial cross-sectional view of a portion of a backmember.

[0119]FIG. 78 is a cross sectional view a back support member.

[0120]FIG. 79 is a partial rear view of a lumbar support member.

[0121]FIG. 80 is a partial cross-sectional view of the seat supported bythe tilt control housing.

[0122]FIG. 81 is an exploded perspective view of a seat adjustmentmechanism.

[0123]FIG. 82 is an exploded perspective view of one embodiment of aseat support assembly.

[0124]FIG. 83 is a partial exploded perspective view of one embodimentof an armrest assembly.

[0125]FIG. 84 is an exploded perspective view of one embodiment of anupper portion of an armrest assembly.

[0126]FIG. 85 is a cross sectional view of one embodiment of an armrestassembly.

[0127]FIG. 86 is a cross-sectional view of one embodiment of an armrestassembly.

[0128]FIG. 87 is front view of an armrest sleeve member.

[0129]FIG. 88 is an exploded perspective view of a backrest assembly.

[0130]FIG. 89 is a side view of a back support member.

[0131]FIG. 90 is a cross-sectional view of the back support member takenalong line 90-90 of FIG. 89.

[0132]FIG. 91 is a front view of a back support member.

[0133]FIG. 92 is a cross-sectional view of the back support member takenalong line 92-92 of FIG. 91.

[0134]FIG. 93 is a side view of a back support fulcrum member.

[0135]FIG. 94 is a partial top view of the back support fulcrum membershown in FIG. 93.

[0136]FIG. 95 is front view of a back member with a cut-out therein.

[0137]FIG. 96 is a front view of the back member shown in FIG. 95 with ahinge portion overmolded thereon.

[0138]FIG. 97 is a partial cross-sectional view of the back member takenalong line 97-97 of FIG. 96.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0139] General:

[0140] The terms “longitudinal” and “lateral” as used herein areintended to indicate the direction of the chair from front to back andfrom side to side, respectively. Similarly, the terms “front”, “side”,“back”, “forwardly”, “rearwardly”, “upwardly” and “downwardly” as usedherein are intended to indicate the various directions and portions ofthe chair as normally understood when viewed from the perspective of auser sitting in the chair.

[0141] Referring to the drawings, FIGS. 11 and 12 show a preferredembodiment of the chair having tilt control housing 10, seat 200, backsupport 304 and back 302. It should be understood that the term“housing” generally refers to any support member that supports anothermember, and includes, but is not limited to a structure that provides anenclosure. A pair of armrests 400 extend from, move with and define aportion of the back support 304. Preferably, the back support 304 ispivotally mounted to the control housing 10, and the seat 200 ispivotally mounted to the back support 304 via a pivot axis located onthe armrests 400 at the approximate hip joint of the user above theseating surface. The seat 200 is further slideably and pivotallysupported by the tilt control housing.

[0142] It should be understood that the terms “mounted,” “connected”,“coupled,” “supported by,” and variations thereof, refer to two or moremembers or components that are joined, engaged or abutted, whetherdirectly or indirectly, for example, by way of another component ormember, and further that the two or more members, or interveningmember(s) can be joined by being integrally formed, or by way of variousfastening devices, including for example and without limitation,mechanical fasteners, adhesives, welding, press fit, bent-over tabmembers, etc.

[0143] In operation, the housing 10, seat 200 and back support 304, withthe armrests 400, form a three-bar linkage with a slide. It should beunderstood that the term “slide,” as used herein, refers to two membersthat translate relative to each other, whether by direct sliding or byrolling. Preferably, the pivot axis formed between the seat 200 andhousing 10 is positioned forwardly of the pivot axis formed between theback support 304 and housing 10, which axis is positioned forwardly ofthe pivot axis formed between the back support 304 and the seat 200,such that the backrest 300 and back support 304 tilt rearwardly at agreater rate and angle than does the seat 200. Preferably, the backtilts relative to the seat at about a preferred 2:1 ratio, such that theshirt-tail pull effect is avoided. Of course, other synchrotilt ratiosare contemplated and suitable. In addition, the configuration of theback support, the seat and the various positions of the pivot axes,allow the seat to pivot about the ankles of a user seated in the chair,preferably without the front edge of the seat rising as the user tiltsrearwardly. The three-bar linkage provides a simple and compactmechanism that avoids the use of additional links. Additionally, byforming the linkage assembly from the seat, back support and housing,complex and expensive links and load bearing parts are avoided.

[0144] An adjustable support column 12, preferably pneumatic and shownin FIG. 42, is mounted to a rear portion of the housing 10 at opening14. A top portion of the column 12, having a side-actuated lever 16,extends into the housing, and preferably is fitted inside a bushing 50that captures and connects the various tilt control housing components.A cable 18 is connected to the lever, and can be moved within a guide toactuate the lever. An opposite end of the cable is engaged by an arm ona pivot tube 22, shown in FIGS. 43 and 60. A grippable handle 24, orpaddle, extends from the tube. In operation, the user rotates the paddle24 and thereby moves the cable 18 to actuate the lever 16, which in turnallows the support column 10 to extend in response to a gas springcontained therein, or to collapse in response to the weight of the userbeing applied to the seat. One suitable support column is available fromSamhongsa Co. Ltd., otherwise referred to as SHS.

[0145] Referring to the embodiment of the adjust mechanism for thesupport column shown in FIGS. 60 and 69, the tube 22 (which is rotated180 degrees in FIG. 60) has a flared end 802. The end 802 of the tube isconfigured to matingly engage a first end 806 of a pivot member 804. Thepivot member 804 has a second end 808 that is rotatably received on ahub 812 of gear 810. A clip 819 secures the end 808 to the hub 812. Thepivot member includes an arm 814 that extends perpendicular from a tubeportion of the pivot member. The arm includes an end portion thatengages end of the cable 18. A spring 816 biases the pivot member to areturn position. In operation, the user moves the paddle 24, whichrotates the tube 23 and the pivot member 804. As the arm 814 of thepivot member is moved, it moves the cable 18 relative to the guide, andthereby actuates the support column.

[0146] Referring to FIGS. 11 and 12, a base 26, preferably a five armbase with casters, is mounted to the bottom of the support column 12 ina conventional manner, although one of skill in the art would understandthat other support columns and bases can be used to support the housing,including fixed height support columns and non-rolling bases, includingfor example a base configured with glides.

[0147] With the chair being generally described, the various features ofthe armrests, the seat, the backrest and the tilt control assembly,along with various controls therefore, will be described in more detailbelow.

[0148] Armrest Assembly:

[0149] Referring to FIGS. 1, 2 and 58-60, one preferred embodiment of anarmrest assembly 400 is shown as having a lower portion 402 and an upperportion 404. The lower portion 402 includes a lower support memberhaving a laterally extending, and substantially horizontal portion 406and an upper spine portion 408 extending upwardly and outwardly from thehorizontal portion 406. The spine portion 408 is preferably curved anddefines a curvature substantially in a plane substantially parallel tothe torso of the user. In one preferred embodiment, shown in FIGS. 1 and2, the spine 408 has a lower curved portion 410 and an upper curvedportion 412, with the upper curved portion having a smallercross-section, which is preferably rectangular, than the lower curvedportion. Preferably, the lower portion is made of 380 cast aluminum orany other suitably strong material, such as metal, including steel, orfiberglass, plastic, composites and other similar materials.

[0150] As shown in FIGS. 1, 2, 71 and 87, a pair of sleeve members 414are disposed on the upper curved portion 412 and define a cross-sectionsubstantially the same as the lower curved portion. Referring to theembodiment of FIGS. 58-59 and 87, notches 413 locate the sleeve members414 on the curved portion 412 by way of a locator tab 415. It should beunderstood that the sleeve members can be made as a single member thatis disposed over the end of the spine 408.

[0151] As best shown in FIGS. 13 and 58-60, the ends of the lowerhorizontal portions 406 extend through openings 306 in opposite sides ofa back support 304 and are secured, preferably fixedly (for example bywelding), one to the other and/or to the back support member.Alternatively, the lower portions can be moveably secured to andsupported by the back support, so as to allow them to move inwardly andoutwardly in the lateral direction. In either embodiment, the lowerportions 402 of the armrests form part of the back support 304. Thelower portions of the armrests can be configured in any number ofshapes, and provide different mounting pivot locations for the seat. Forexample, the shape and size of the armrest can be varied to providedifferent mounting arrangements and locations for the seat.Alternatively, a single modular armrest can be configured with aplurality (meaning two or more) mounting arrangements on the samemember. In the preferred embodiment, the spine portion of the backsupport 304 can be made as a modular element, with the overallconfiguration of the back support being quickly and easily reconfiguredsimply by providing a different lower portion of the armrest.

[0152] Referring to the embodiments shown in FIGS. 1 and 71, an opening416 is formed through the upper curved portion 404 and is shaped toreceive a pivot member 418, 818, which secures the seat 200 to the spine408, as shown in FIGS. 15 and 71.

[0153] Referring to FIGS. 2 and 87, the sleeve members 414 arepreferably U-shaped, having an inner and outer wall 420, 422 joined byan end wall 424. In the embodiment shown in FIG. 2, a cut-out 426 in theinner wall is shaped to receive the pivot member 418 once the sleevemembers 414 are installed on the upper portion of the spine. Referringto the embodiment of FIG. 87, the inner wall is formed from a pluralityof flexible tab members. Some of the tab members 417 have an innersurface that is raised above the surface of other of the tab members419. The tab members are biased against the curved portion 412 and takeup the tolerances.

[0154] Referring to FIGS. 2-4, 71 and 87, a rack 428 is formed on theouter wall 422. The term “rack” as used herein broadly means a series ofengageable elements, including for example and without limitation,teeth, grooves, slots, openings, protuberances, etc. Referring to FIGS.3 and 4, the profile of the rack 428 includes a plurality of curvedengagement portions 430, and a plurality of teeth portions 432interspaced between the curved portions, with a plurality of slopingrecesses 434 and slots 436 defining the profile of the rack, whichprovides unique positions for positive latch engagement.

[0155] Referring to FIGS. 71 and 87, the profile includes a plurality offirst and second recesses 435, 437. Preferably, the profile extendslaterally across the entirety of the face of the outer wall 422. In onepreferred embodiment, the sleeves are made of acetal.

[0156] Referring to FIGS. 2 and 87, one of the sleeve members 414(female) has a plurality of recesses 438 formed in the end of the freeedge 442 of the inner and outer walls, while the other sleeve (male) hasa plurality of protuberances 440 extending from the end of the free edge442, with the protuberances 440 shaped to be received in the recesses438 when the free edges 442 are abutted as the sleeve members 414 areinstalled on the spine 408. In this way, the sleeve members 414 areprevented from moving longitudinally relative to one another along thespine.

[0157] Referring to FIGS. 3 and 4, in one preferred embodiment, thesleeve members 414 each include a flange 444 formed along the free edgeof the outer wall, with the recesses or protuberances formed in the faceof the flange. The outer edge 446 of the flange includes a plurality ofindexing notches 448 that form a rack 450 and are spaced longitudinallyalong the flange approximately the same distance as the engagementportions 430 of the rack 428.

[0158] Referring to FIG. 2, the sleeve members 414 each include aplurality, meaning two or more, bearing pads 452 on the end walls andinner walls that extend outwardly from the wall and slidably engage thecurved upper members 404. Alternatively, the sleeves can include rollerbearings that engage the curved member.

[0159] In one preferred embodiment, the radius of the inner surface ofthe lower curved portion 410 and of the inner wall of the sleeve members414 is approximately 13.78 inches, while the radius of the outer surfaceof the lower curved portion 410 and of the outer wall of the sleevemember is approximately 14.68 inches. Of course, it should be understoodthat other radii would also work, and that preferred radius is betweenabout 12 and about 16 inches.

[0160] Referring to FIGS. 1, 2, 15 and 83, the upper portion 404 forms astem 454 that includes a housing 456 forming a cavity 458, which isshaped to receive the curved spine 408 and sleeve member 418. The cavity458 is defined by an inner and outer wall 460, 462, and a pair of endwalls 464. The stem 454 has approximately the same curvature as thespine 408, such that it can slide therealong without binding. Forexample, in one preferred embodiment, the radius of the inner surface ofthe outer wall 462 of the cavity is approximately 14.73 inches, andpreferably between about 12 and 16 inches. An elongated opening 416, orslot, is formed in the inner wall 460 and is shaped to receive the pivotmember 418, such that the stem 454 can be moved relative to the spine408 without interfering with the pivot member. An opening 466 is alsoformed in the outer wall 462 so as to expose the racks 428 of the sleevemembers disposed on the spine.

[0161] Referring to FIGS. 2-4, 83 and 85, a latch mechanism 468 ispivotally secured to the outer wall 462 of the stem and is received inthe opening 466. Referring to the embodiment of FIGS. 2-4, the latchmechanism 468 includes a lever member 470 and an index member 472pivotally mounted to the stem 454 with a pivot pin 474 at asubstantially horizontal pivot axis. The index member 472 is nested orpocketed in the lever member 470, as shown in FIGS. 3 and 4. It shouldbe understood that the lever and index member can be integrally formedas a one-piece member. In the embodiment of FIG. 83, the index member isomitted. Referring to FIGS. 2 and 83, the lever member 470 includes agrippable handle portion 476 that extends downwardly from the pivot axisand is nested in a recess 478 formed in the stem. The recess 478 extendsbelow the end of the lever so as to allow the user to insert a fingerand grip or lift the lever member 470 from an engaged position to moveit to a disengaged position. Referring to FIGS. 3, and 4, the levermember 470 further includes an engagement portion 480 that extendsinwardly and engages one of the curved engagement portions 430 of therack when the lever is in the engaged position. The engagement portionhas a curved surface that translates relative to the sloping surface ofthe recess 434 as the lever is moved between the engaged and disengagedpositions. The lever has a cavity 482 shaped to receive the index member472 and includes a pair of shoulders 484 that mate with and abutcorresponding shoulders 486 on the index member, such that the indexmember is pivoted about the pivot axis 474 with the lever member.

[0162] Referring to FIGS. 83, 85 and 86, a primary engagement portion481 is shaped to be received in the recess 435, while a secondaryengagement portion 483 is received in the recess 437. The lever furtherincludes a stop portion 485 that engages an upper edge 487 of the stemwhen the lever is in the unlatched position. A spring 491 is disposedabout the pivot pin 474 and is engaged between the lever 470 and thestem 454 so as to bias the lever to an unlatched position. The lever 470acts as an over-center toggle, such that it snaps into the latchedposition when it is moved into engagement with the rack. A portion ofthe lever and/or a portion of a spring can index with the rack as theupper arm portion is moved to the desired position.

[0163] Preferably, the lever 470, sleeve members 414 and stem 454 aremade of a SG95 or SG200 Urethane, 79-80D Durameter. Alternatively, thosecomponents can be made from various plastics, metals, elastomers,composites, fiberglass, etc.

[0164] Referring to the embodiment of FIGS. 2 and 3, the index memberincludes a bumper portion 488 having a concave surface shaped to engagethe curved portion 430 when the lever is in the engaged position.Preferably, the index member 472 is made of 2140 Urethane, 55-65DDurameter, although it should be understood that it can be made of otherplastics, metal, fiberglass, rubbers, composites and the like, orcombinations thereof. The index member 472 further includes a flexible,resilient indexing finger 490 that extends outwardly from the indexmember. The indexing finger 490 is disengaged from the rack 450 when thelever is in the engaged position. As the lever 470 is moved to thedisengaged position, the indexing finger 490 is pivoted into abutmentwith the flange 444 of the sleeve, and selectively engages the notches448 of the rack 450 as the stem 454 is moved relative to the spine 408.The indexing finger 490 will selectively engage one of the notches 448as the lever is moved from the engaged to the disengaged position andbefore the stem is moved relative to the spine. As the stem is movedrelative to the spine, the indexing member 472 successively, selectivelyengages the notches 448 and provides an audible indexing sound toindicate to the user that an available vertical position has beenselected. The lever 470 can then be pivoted from the disengaged positionto the engaged position to again secure the stem 454 to the spine 408and prevent movement therebetween.

[0165] It should be understood that the racks could be formed on thestem, and with the lever and/or indexing members pivotally mounted tothe spine.

[0166] Referring to FIGS. 1, 2, 6-10 and 83, the upper portion 404 ofthe armrest assembly provides lateral and pivotable adjustment of anarmrest. Referring to FIGS. 2, 6 and 83, the upper end of the stem formsa mounting platform 492, which has a guide member 494, or pivot member,extending upwardly therefrom and defining a substantially vertical pivotaxis 504. The term “platform” as used herein means any support structureor surface, and includes, but is not limited to, a substantially flat,horizontal member or surface, or platelike member. In addition, aprotuberance 496, or detent extends from the mounting platform 492 at alocation spaced from the guide member 494. The detent can be springloaded.

[0167] Referring to FIGS. 2, 6-10 and 84, a support platform 498includes an opening 500 that is shaped to receive the guide member, withthe platform disposed on the guide member at the opening such that theplatform can pivot about the pivot axis. Referring to the embodiment ofFIGS. 2 and 6-10, the platform 498 includes a plurality of recesses 502formed on a bottom surface thereof and spaced from the opening so as tobe aligned with the protuberance. The plurality of recesses 502 form anarray thereof having a curvature generally centered around the pivotaxis 504.

[0168] In the embodiment of FIG. 84, the protuberance 496 extendsthrough an opening 503 formed in the platform and is indexed in a slot505 formed in a platform 506 by a pair of arms 507 that have endportions 515 that are shaped to define three openings 509. Of course,more openings could be formed and defined by the slot and arms. A rubberor elastomeric spring 511 is disposed in a slot 513 formed opposite slot505. The spring 511 biases the arms 507 against the protuberance.

[0169] In operation of the embodiment shown in FIGS. 2 and 6-10, theplatform 498 is moved or pivoted about the pivot axis 504 relative tothe mounting platform 492, with the protuberance 496 indexing with oneof the plurality of recesses 502 so as to locate the platform 498relative to the mounting platform 492 in a plurality of pivot positionscorresponding to the plurality of recesses. In the operation of theembodiment shown in FIGS. 84, the platform is moved or pivoted about thepivot axis 504 relative to the mounting platform 492, with theprotuberance 496 indexing with one of the plurality of openings 509 soas to locate the platform 498 relative to the mounting platform 492 in aplurality of pivot positions corresponding to the plurality of recesses.A bearing member can be disposed on the protuberance, with the bearingmember indexing with the openings.

[0170] It should be understood that the location of the recesses (oropenings) and protuberance can be reversed, with the protuberanceextending downwardly form the platform and with the array of recesses oropenings formed in the mounting platform on the top of the stem.Likewise, it should be understood that an array of protuberances couldbe provided on one or the other of the platforms and which mate with arecess.

[0171] Referring to FIGS. 2 and 84, the first platform 498 is secured toanother second platform 506. As shown in one embodiment of FIG. 8, theplatform 506 has a recess formed in a bottom portion thereof that isshaped to receive the raised indentations 510 that form the array ofrecesses 502 on the bottom side of the platform. Referring to FIGS. 2and 84, the platform 506 has an opening 512 formed on one end thereofthat is shaped to receive the guide member 494. A second opening 514,516 is formed on an opposite end of each of the platforms 506, 498.Referring to FIG. 2, fastener 518 extends through the second openingsand secures the platforms one to the other. Alternatively, a boss can beformed on the platform 498, with the boss extending into a boss formedin platform 506 and through opening 514. A fastener, and one or morewashers, extends downwardly through the platform 506 and is engaged withthe boss to secure the platforms 498 and 506 together.

[0172] In a first embodiment of the platform 506, shown in FIG. 2, theplatform includes a recess or channel 520 formed across an entire widththereof. A pair of spaced apart and parallel linear gears 522, or racks,define the opposite side walls of the channel. An armrest support 526,shown in FIGS. 2 and 7, includes a pair of axles 528 that define a pairof spaced apart axes of rotation. A pair of pinion gears 524 are mountedto the armrest support on the axles 528 and are disposed in the channel520, such that each of the pinion gears mesh with each other and one ofthe linear gears 522 respectively.

[0173] In a second embodiment, shown in FIGS. 6, 8 and 84, the platformhas only a single linear gear 522, with an opposite wall of the channel520 being preferably substantially smooth. The armrest support has onlya single axle 528 defining an axis of rotation. A single pinion gear 524is rotatably mounted on the axle 528 within the channel and meshes withthe linear gear 522.

[0174] In either embodiment, as shown in FIGS. 2, 6, 8 and 84, thearmrest support 526 includes a pair of spaced apart and substantiallyparallel tracks 530, shown as slots, formed therethrough. One of thetracks 530 receives the guide member 494 extending upwardly from thestem through the platforms 498, 506, while the other receives a guidemember 532 formed on an upper surface of the platform 506, and throughwhich the fastener 518 passes to secure the platforms 498, 506. Inoperation, the user moves the armrest support 526 laterally relative tothe platform 506, such that in one preferred embodiment, the piniongears 524 mesh with each other and with the linear gears 522, or inanother preferred embodiment, the single pinion gear 524 meshes with thesingle linear gear 522, as the guide members 494, 532 ride in the tracks530. The interaction between the pinion gear(s) 524 and linear gear(s)522 provides a firm solid feel as the armrest support 526 is moved inthe lateral direction and is guided by the guide members riding in thetracks. In the embodiment of FIGS. 6, 8 and 84, the platform 506includes an additional pair of guides 534, configured as posts, thatextend upwardly therefrom and are received in a track 536 or channelformed in the armrest support 506.

[0175] It should be understood that the various guide members and trackscould be formed in either the platform or armrest support. Likewise, thechannel and linear gear(s) could be formed in the armrest support, withthe pinion gear(s) secured to the platform. Also, it should beunderstood that the upper and lower platforms 498, 506 can be made as asingle, one-piece member, with the recesses or protuberances formed onone side thereof, and with the channel and linear gear(s) formed on theother side thereof.

[0176] Referring to FIGS. 2, 9, 10 and 84, a pawl member 538 is shown asbeing pivotably mounted to the armrest support 526 about a pivot axis540. The pawl member can be secured to the pivot member 540 with aretainer member. In the embodiment of FIGS. 2 and 10, the pawl 538includes a first arm 542 having an end portion 544 defining one or moreteeth or engagement portions that are shaped to engage one or more teethon one of the pinion gears 524. Preferably, the pawl is pivotallymounted to a top surface of the support 526, with the end portion 544extending through an opening 545 in the support to engage the one ormore teeth on the pinion gear(s). The pawl further includes an opening546, elongated or circular, formed opposite the end portion and a secondarm 548 extending substantially perpendicular to the first arm.Referring to the embodiment of FIG. 10, a track 550 or slot having aradius about the pivot axis 540 is formed in an end portion of the arm548 and is shaped to receive a post or guide 552 extending upwardly fromthe armrest support.

[0177] A push button 554 includes a flange portion 556 that is slideablymounted in a pair of tabs that form a track 558. The button has an armextending from the flange that includes a post 560 received in theopening 546 of the pawl. A spring 562 is mounted to the armrest supportand biases the end portion 544 of the pawl into engagement with at leastone of the teeth on at least one of the pinion gears 524. Alternatively,or in combination therewith, a pair of springs 549 bias the push buttonaway from the platform as they engage a pair of backstops 551.

[0178] In the embodiment of FIGS. 9 and 84, the pivot axis is formed atthe junction of the first and second arm 538, 542, with the post 560engaging the opening 546 or track in an end portion of the arm 548.

[0179] In the operation of either embodiment, the user pushes the pushbutton 554 inwardly as it slides within the track 558 so as to move thepost member 560 laterally inward. The post member 560 rotates the pawl538 against the force of the spring 562, 549 about the pivot axis 540and moves the end portion 544 thereof away from the teeth of the piniongear(s) 524 to a disengaged position. When the desired lateral locationof the armrest support is reached, the user releases the button 554,thereby allowing the spring 562, 549 to bias the pawl 538 to an engagedposition with at least one of the pinion gear(s) 524. In the engagedposition, the pawl 538 prevents the pinion gear(s) 524 from rotatingabout the axis, so as to prevent the armrest support 526 from beingmoved in the lateral direction.

[0180] It should be understood that a lever or actuator other than thepush button can be employed to move the pawl from the engaged todisengaged position. Likewise, it should be understood that the pawl canbe moved along a linear, rather than a rotational, path between theengaged and disengaged positions.

[0181] Referring to FIG. 2, a fastener 564 secures the armrest support526 and the platforms to the guide member 494 and stem 454. In this way,the armrest support 526 pivots with the platforms 498, 506 about theguide member 494 as the armrest support is moved to the desired pivotposition. A pad 566, preferably foam, and substrate 568 are secured tothe armrest support with various fasteners and/or adhesive. The pad alsocan include various gels or other fluids and/or gases to provide acomfortable feel to the user's arm, which rests thereon. Preferably, thepush button, or other actuator, is received in an opening or recessformed in the pad, and is configured with an outer contour shaped tomate with the outer contour of the pad.

[0182] Backrest:

[0183] Referring to FIGS. 11-13 and 23-32, a first embodiment of abackrest 300 includes a backrest frame member, or back support member304, and a back member 302. The support member 304, otherwise referredto as a frame member, includes a lower support member 308 having a pairof forwardly extending arms 310 that are pivotally connected to the tiltcontrol housing 10.

[0184] As best shown in FIGS. 40, 58 and 60, the arms 310 are preferablysupported on a pivot member 317. Referring to FIG. 50, in one preferredembodiment, the pivot member 317 has a pivot portion 312 having a firstdiameter, a flange 314 formed on one end thereof and an insert portion316 having a second diameter less than said first diameter. The flange314 or head engages or traps the lower support member arm 310. Theinsert portion 316 is press fit into a pivot tube 318 with aninterference fit. The pivot tube 318 extends through an opening formedin the side wall 28 of the housing. As the insert portion 316 is pressfit into the tube 318, it deforms or swages the ends of the tube againstthe side wall 28 to form a fixed joint therebetween, but allowing thesupport member 304, and in particular the arms 310, to freely pivot onthe pivot portion 312 of the insert member. In this way, a simplepress-fit operation secures the back support member 304 to the housing10. Of course, it should be understood that other seating components,such as the seat, could also be secured to the back support or housingin this manner. The pivot portion 312 of the pivot member can belengthened to accommodate springs as further explained below.

[0185] Referring to FIGS. 13, 43 and 58-60, the lower support member 308further includes a pair of openings 306 that receive the lower portionsof the armrest as previously explained. In the embodiment shown in FIGS.13 and 43, the lower support member 308 further includes a supportmember 320 extending laterally and substantially horizontally betweenopposite sides thereof for engagement with a pair of leaf springs 30, aswill be explained in more detail herein below.

[0186] As shown in FIGS. 23, 39, 43, 58-60, 73 and 88, a rear portion ofthe lower support member forms an upwardly extending arm 322. An uppersupport member 324, or spine, has a lower end 326 that mates with and issecured to the arm 322 with a pair of fasteners 327. A cover can bedisposed over the fasteners to provide a smooth, aesthetic appearance.By making the support member 304 in two-pieces 308, 324 the backrest canbe disassembled and the chair can be shipped in a smaller package. Inparticular, the arm 322 of the lower backrest support preferably doesnot extend upwardly above the uppermost surface of the armrests, suchthat the base, seat and armrests can be compressed to a relatively shortheight. In turn, the backrest 300 can be easily assembled by the enduser with a pair of fasteners. Moreover, the backrest can be madeoffline, if desired. As shown in FIGS. 24, 25, 73 and 88, the lower end326 of the spine flares outwardly and defines a pair of oppositelandings 328 that mate with the back member 302.

[0187] The spine 324 extends upwardly and has a pair of arms 330 thatextend upwardly and outwardly from an upper end thereof. The ends of thearms each have a pad 332 that is secured to the back member 302 with afastener. In particular, as shown in FIGS. 32 and 88, a boss 303 extendsfrom the rear of the back member and supports the pad and receives thefastener. A front surface of the spine has a rack 334, or a plurality ofnotches formed thereon.

[0188] The spine is preferably made of aluminum, steel, fiberglass,composites, plastic, or some other rigid but resilient material. Asshown in the embodiment of FIGS. 73 and 88, the rack 334 is formed on alumbar support insert 820, which is secured to the front side of thespine with a plurality of fasteners 822. The lumbar support insert 820and spine can be made of various materials, such as Capron 8233G—33%Glass Filled Nylon 6.

[0189] Referring to FIGS. 73, 78 and 88, in one preferred embodiment,the spine 324 has a plurality of forwardly extending fins 821, while thelumbar support insert 820 has a plurality of rearwardly extending fins823 that are shaped to be inserted or nested in the spaces formedbetween the plurality of fins 821. In this way, the spine and insert arevery strong and resistant to bending, yet provide substantiallytorsional flexibility. In addition, the two pieces can be easily madefrom molded plastic, with thinner walls and less material. In addition,the insert 820 and spine 824 can be spaced apart along the sides thereofto form a gap.

[0190] Referring to FIGS. 23, 28-32, 73, 74, 88 and 95-96, the backmember 302 is preferably made of a resilient, compliant material,including various polymeric or plastic materials. For example, in onepreferred embodiment, the back member is molded of a polypropylene 76523Montel Profax material. The back member 302 has a top 336, a bottom 338and opposite, curvilinear sides 340. The sides 340 preferably have aconcave, or hour-glass shape. The top 336 of the back member ispreferably curved and has a convex front, body-supporting surface 342along a peripheral portion thereof.

[0191] The back member has a lumbar region 344, a thoracic region 346and a lower region 348. The lower region includes a cut-out 350 shapedto be received on the lower end 326 of the spine, with a pair of bosses352 positioned to mate with holes formed in the landings 328. The lowerregion also includes a sacral support 329, formed by a forwardlyextending portion at the center of the lower region, as shown in FIGS.32, 30 and 73. A pair of fasteners secure the bottom of the back member302 to the landings 328. The back member 302 has a plurality of openings354 formed therethrough. Preferably, an array of openings in the lumbarregion 344 are elongated in the longitudinal direction, which runsbetween the top and the bottom of the back member. The openings 354 arepreferably staggered. For example, in one preferred embodiment, adjacentvertical columns of openings are offset in the vertical direction, suchthat the openings in adjacent columns are not horizontally aligned.

[0192] As with the lumbar region 344, the thoracic region 346 alsoincludes an array of staggered elongated openings 354. Preferably, theelongated openings formed in the thoracic region are not as elongated,on average, as the openings in the lumbar region. This means, of course,that an occasional opening, or plurality of openings, in the thoracicregion can have a greater elongation than an opening or plurality ofopenings in the lumbar region.

[0193] Likewise, the lower region 348 has an array of staggeredelongated openings 354 formed therein, again, with an average elongationless than that of the lumbar region.

[0194] Referring to FIGS. 74, in one alternative embodiment, theelongated openings 355 in the lower region transition from alongitudinal orientation to a lateral orientation, with the transitionbeing made progressively lower as it moves from a center line outboard,so as to form a generally triangular region of lateral openings. Some ofthe openings are curved to make the transition.

[0195] The elongated openings in the lumbar region and the adjacenttransition areas of the thoracic and lower regions are preferablyobround 356. The shapes of the openings then transition from the obroundshape to a peanut-shaped opening 358 as the location thereof movesupwardly and downwardly from the lumbar region, and then eventually thepeanut-shaped openings are closed at a middle thereof to formsubstantially circular openings 360 adjacent the top and bottom of theback member. In addition, smaller circular openings 362 are formed alongthe opposite sides of the back member, including at the lumbar region,and around the entire peripheral portion of the back member. In theembodiment of FIG. 74, the openings in the lower region do nottransition to a peanut shape, but rather preferably stay obround, withan outer perimeter of circular openings 362.

[0196] The back member 302, especially in the lumbar region, alsopreferably has a first thickness along the center line 364 thereof, anda second thickness at the peripheral sides 366 thereof, with the secondthickness being greater than the first thickness, as shown for examplein FIG. 30. For example, in the lumbar region, one preferred firstthickness is about 2 mm, and one preferred second thickness is about 3mm. As shown in FIGS. 29 and 32, the back member is preferably bowedforwardly at the lumbar region 344. As shown in FIG. 77, the edge of theback member preferably is formed as a bead 345. The back member ispreferably formed by molding.

[0197] Referring to FIGS. 27, 72, 73 and 79, a first back supportconfiguration includes a lumbar support 368 having a lumbar frame member370, configured as a bow spring having a center portion 372 and oppositeends 374. The center portion 372 includes a guide member 376 thatinterfaces and slides on a track 378 formed along a portion of thelength of the spine, as shown in FIG. 24.

[0198] In the embodiment shown in FIGS. 72, 73 and 78, the guide 376includes a plurality of hook members 824 that engage and slide along thesides 826 of the lumbar support insert 820. Preferably, the hook members824 extend through the gap 829 formed between the spine 324 and theinsert member 820. In one preferred embodiment, the center portion 372or guide member further includes a spring detent 380 that is engagedwith the rack 334 to releasably secure the lumbar support 368 in aplurality of vertical positions. Other devices, such as set screws, pawlmechanisms, latches, friction cams and the like can be used to securethe lumbar in various positions.

[0199] Referring to FIGS. 72, 73 and 79, a knob 382 is rotatably mountedin each end of the bow member. The knob 382 includes a mountingarrangement, such as a retainer 829 having an opening offset from theaxis of rotation of the knob. A lumbar belt 384 extends between the endportions 374 and is secured to the knobs 382 with a fastener 828 at theoffset opening. The belt engages and supports a rear surface of the backmember. The knobs 382 can be rotated, which rotates the fasteners 828,to thereby put the strap 384 in tension and increase the amount oflumbar support. The retainer 829 holds a detent 830 in engagement with acircumferential rack 833 formed along the inside of the opening in thebowed frame 370, such that the knob 382 can be indexed in a plurality ofrotational positions.

[0200] The lumbar frame member and strap are preferably made of nylon,but can be made of other materials, such as metal, wood, composites,fiberglass, plastics and the like. The strap preferably includes aplurality of staggered, elongated openings 354 formed therethrough. Oneor more lumbar pads can be attached to the strap, or disposed betweenthe strap and the back member.

[0201] Referring to FIGS. 88-94, a second back support configurationincludes a first support member 1300 and a second support member 1302.In one preferred embodiment, the first support member 1300 is formed asa loop having a base 1304, a pair of arms 1306 and a support band 1308or belt extending between the two arms 1306. The support band has aforwardly facing surface 1310 that engages and supports a rear surfaceof the back member 302. A downwardly opening recess 1312 or pocket isformed in the middle portion of the belt, as best shown in FIG. 92. Therecess 1312 forms a guide or track for a portion of the second supportmember 1302.

[0202] As best shown in FIGS. 88-90, the second support member 1302 hasa J-shape, with a base arm 1314 connected to a support arm 1316 havingan end 1318, which is shaped and configured to be received in the recess1312 of the second support member. The bottom of the J-shaped supportmember 1302, or a curved portion 1328 forms a free end of the supportmember 1302. The end 1318 of the support arm is supported by the lumbarsupport 1300 as it slides vertically in the recess, so as to allow thefirst and second support members to function independently. At the sametime, the loop supports the support arm 1316 laterally and in thefore/aft direction. Alternatively, the end 1318 of the support arm 1316can remain unsupported, or it can be fixedly connected to the supportmember 1300, of lumbar support, or to the frame.

[0203] The base arm 1314 has an upper end 1320 disposed between the baseof the first support member and the lumbar insert member. A fastenersecures the first support member 1300 and the second support member 1302to the insert member 820. The arms 1314, 1316 of the second supportmember, once installed, function as a cantilevered spring, which issupported at ends 1302 and 1318 and has free end 1328. The base arm 1314has a plurality of longitudinally extending and rearwardly facinggrooves 1322, 1324, which define a plurality of ridges. The base arm1314 also has a step 1326 formed at the bottom thereof, which isconnected to the curved portion 1328 that transitions to the support arm1316 and provides additional flexibility between the arms 1314 and 1316.In this way, the overall support member 1302, including both arms actingin concert, functions as a cantilevered spring, while the individualarms 1314, 1316 act as individual springs that provide additionalindependent flexibility.

[0204] Referring to FIGS. 78, 88 and 93-94, a fulcrum member 1330 isdisposed between the insert member 820 and the base arm 1314 of thesecond support member. The fulcrum member includes a base portion 1344forming a cavity 1348 that substantially surrounds and conforms to theforward surface of the insert member 820. The base portion includes aplurality of hook members 824 that engage and slide along the sides 826of the lumbar insert support member 820. Preferably, the hook membersextend through the gap 829 formed between the spine and the insertmember. In one embodiment, the fulcrum member further includes a detentor latch member that engages the rack to releasably secure the fulcrummember in a plurality of vertical positions. Alternatively, or incombination, the fulcrum includes a guide member 1332 or ridge formed inthe cavity 1348 that rides in a groove 1334 formed in the spine insertmember. In one embodiment, the fulcrum member includes a pair of handles1336. The handles extend outwardly and downwardly and include agrippable portion 1338, formed form example as a plurality of annularridges, on the ends thereof. The front portion of the fulcrum memberinclude a pair of guide members 1340 or tabs that ride in the outerchannels 1322 formed in the base support arm. The fulcrum, first supportmember and second support member are preferably made of one or moretypes of plastic, such as nylon or glass-filled nylon, but can be madeof other materials, such as metal, wood, composites, fiberglass and thelike.

[0205] It should be understood that in an alternative embodiment, one orall of the sacral support member, the lumbar support member and thefulcrum member can be connected to the back member and engage the frame.

[0206] In operation, the user grips one or both of the fulcrum handles1336 and moves the fulcrum in the vertical direction to a desiredposition. As the fulcrum is lowered, it shortens the cantilevered lengthof the support member 1302, i.e., the distance between the fulcrum andthe bottom curved portion 1328, and the arms 1314, 1316 in particular,and provides a firmer, more rigid support for the lower region 348 ofthe back member as it engages the rear surface thereof. The user canraise the fulcrum 1330 so as to provide a greater cantilevered length,which in turn provides more flexibility of the support member and acorresponding less rigid support of the back member in the lower region.

[0207] Referring to FIGS. 95 and 96, the back member 302 can be modifiedto improve the flexibility of the lower region thereof. In particular, aU-shaped cut-out 1350 can be made in the lower region, for example alongone row of openings 354 as they transition from the vertical to thehorizontal. In this way, the lower region 348 is provided with a centralflap 1352 or support region at the sacral region of the user's back,which is spaced from a firmer lower portion 1356. The back member isthen inserted into a mold, wherein a hinge portion 1354 is overmolded onthe back member over the cut-out so as to flexibly connect the flap 1352with the lower portion 1356 of the back member. In one embodiment, thehinge 1354 is formed as a living hinge, with a bellows shape. Of course,it should be understood that the hinge can be in-molded in the originalback member, which thereby avoids the cutting and overmoldingoperations. In addition, it should be understood that the back membercan be provided with greater flexibility by providing a thinner materialin certain regions, or by providing other hinge type devices, notlimited to a living hinge or molded hinges. In this way, the flapportion 1352 of the lower region 348 of the back member being acted uponby the support arm 1316 of the first support member is provided withgreater flexibility to move in response to the position of the supportmember 1302 as the fulcrum member is moved to a desired position. In oneembodiment, the hinge is formed from an elastomeric material, such as athermoplastic elastomer.

[0208] The configuration of the spine 324 and back member 302 providesmany advantages. For example, the compliant back member 302, with itslarger, or longer, openings in the lumbar region, and its lesserthickness along the center portion, allow that region to be moreflexible, such that it can be formed and supported by the lumbar supportand/or sacral support. In addition, the entire back is allowed toconform to the back of the user, and in particular at the edge portionsthereof, and can flex about the center spine in torsion, which is mademore flexible by way of the two-piece construction with nested fins, andalso about the bowed lumbar region. In essence, the intelligence of thebackrest is shared by the spine 324 and the back member 302. In thisway, the backrest provides greater comfort than a backrest formed with aperipheral, and relatively stiff or non-compliant, frame. In addition,by securing the back member 302 to the arms of the spine at a locationspaced below the top of the back 336, including at about 14 inches inone embodiment, and preferably between about 2 inches and about 12inches, and more preferably between about 4 inches and about 8 inches,the top peripheral portion can flex in response to movement from theuser's shoulder and neck and further avoids a “hammock” effect betweenthe top and bottom of the backrest.

[0209] In addition, the spine member is in essence modular, or providesa mounting configuration, which allows the manufacturer to installvarious support configurations on the same spine. In this way, forexample, different back supports can be configured to mount on the samespine to provide an adjustable lumbar support, or a lumbar support withan adjustable sacral support. Of course, other adjustment configurationswould be suitable.

[0210] Referring to FIGS. 33-38, an alternative preferred embodiment ofthe backrest is shown. In this embodiment, the upper portion of thespine 324 is formed as a pair of opposite shoulder portions 386, orears. The shoulder portions 386 preferably are formed as loops thatextend upwardly, outwardly and forwardly from the center spine 324.Preferably, the outermost portion of the shoulders 386 extends forwardlythe greatest amount and forms a forwardly facing and forwardly openingcavity or recess 388 with the center portion of the spine. The lower endof the spine 326 is mated with the lower support member as explainedabove. A lumbar support 368 is mounted to the forward face of the spineas explained above. The lumbar support is substantially the same aspreviously described, except that the lumbar belt or strap 384 has agreater height so as to provide a support over a greater vertical area.

[0211] Referring to FIGS. 33-35, a fabric member 390 is shown as havinga front web 392 with a front, body-supporting surface and a rearsurface. The fabric member has a top, a bottom and opposite sides, whichare preferably curved and have an hour-glass shape. The top preferablyis curved slightly downwardly in the middle thereof between theshoulders. A rear web 394 is secured to the front web along a seam 398that defines the periphery of the fabric member. The front and rear webscan be made of separate materials, or can be made from a single piece ofmaterial. The front and rear web form an upper and lower pocket 396,397. The fabric member is preferably made of a polyester material,although it should be understood that it can be made of any type offlexible, woven, molded or non-woven materials, including variouselastomeric materials and yarns.

[0212] The shoulder portions 386 of the frame member are received in theupper pocket 396, the periphery of which is shaped to mate with andconforms to outer periphery of the shoulder portions. A lower framemember 389 is disposed in the lower pocket 397 and is attached to thelower end of the spine 324. As the lower frame member is secured to thespine, the fabric member 390, and in particular the front web 392, isput in tension and is stretched tight between the lower frame member389, the shoulder portions 386 of the upper frame member and the lumbarsupport 368. Because of the unique shape of the shoulder portions 386and spine 324, the fabric member 390, and in particular the front web392, is suspended in front of the cavity 388 and is free of contact onthe rear side thereof along substantially the entire thoracic region,thereby providing the user with a unique suspension feel. In addition,the fabric is inexpensive to manufacture, and can be easily changed ifdamaged, or if a different aesthetic is desired. Moreover, the spineacts as a torsion spring, and the shoulder portions as springs, toprovide a resilient feel to the user. The lumbar support 368 engages therear side of the front web 392 and provides support for the user's lowerback.

[0213] Seat:

[0214] Referring to FIGS. 11-17, 71 and 82, the chair includes a primaryand an auxiliary seat support 202, 204. A pair of support brackets 206are secured through slots 208 in the primary seat support. Each supportbracket 206 includes a support member 210 that extends upwardly abovethe primary seat support 202 and the seating surface of the membrane 212supported thereby. The support member 210 is secured to the armrestspine with the pivot member 418, 818, which extends through the openingin the stem. A cover 832 can be disposed over the seat support bracket.The pivot member 418, 818 is located at the approximate hip joint of theuser, as further explained in U.S. Pat. No. 6,059,368, which is herebyincorporated herein by reference.

[0215] In a preferred embodiment, shown in FIG. 71, a socket member 834is secured in the support member 210. A ball member 836 is disposed onthe end of the pivot member 818, and is matingly engaged with the socketmember 834, so as to allow rotation of the ball member relative to thesocket member about multiple axes. The opposite end of the pivot member818 is threadably engaged with a nut member 838, which is secured,preferably by welding, to the arm spine 408.

[0216] Referring to FIGS. 15 and 16, in one alternative preferredembodiment, a C-shaped bushing 214 is mounted in an opening 216 formedin the support member, preferably with a snap-fit. The bushing ispreferably made of acetal. The pivot member 418 preferably includes aflat spot 218 and an outer circumferential surface 220. Duringinstallation, the seat is initially rotated such that axle 222 of thepivot member can slide through a mouth 224 of the bushing 214 byaligning the flat spot 218 substantially perpendicular to the mouth 224.The axle 222 has an outer arced pivot surface 236 and a key surface 228defined by the flat spot 218. The pivot surface 226 is defined by aradius “r” from the center 230 of the axle, with the overall axle havinga diameter “D” defined there across. The key surface is formed at adistance “d” from the center of the axle, which is preferably less thanthe radius, and preferably parallel to a plane through the center 230.Preferably, the distance between the key surface 228 and the center 230is less the width of the mouth 224 minus the radius “r” of the axle suchthat the axle can be inserted through the mouth. Once the pivot member418 is located in the bushing, the seat 200 can be rotated to its normaloperating position, wherein the axle 222 is trapped by the bushing 214.In this way, the seat can be secured to the armrest without the use ofany tools, and without having to tighten or manipulate any mechanicalfasteners, which can be expensive and time consuming. Alternatively, theseat and armrest, or back support, can be coupled using any conventionalpivot member. Conversely, it should be understood that the arrangementdescribed herein can be used to secure any two components, not limitedto the seat and back support, in a pivotal configuration.

[0217] Referring to FIGS. 17-19, 41 and 82, the primary and auxiliaryseat supports 202, 204 define a peripheral rim 232 that defines agenerally open center. The primary seat support 202 includes opposite,downwardly extending, and inwardly sloping side support walls 234 thattransmit the load from the seat support to the tilt control housing 10.In the embodiment of FIGS. 17-19 and 41, a pivot member 236 extendsbetween the support walls. A pair of rollers 238 are rotatably mountedon the pivot member 236 adjacent each side wall. It should be understoodthat preferably the rollers can be pivotally mounted on the axle, theaxle can be rotatably supported by the seat, or both. Alternatively, asshown in FIGS. 80 and 81, a pair of pivot members 237 are each insertedthrough a roller 239 and are mounted to a bracket 248. In particular,the pivot member includes a flange that engages one side of the bracket,while a nut 241 or fastener engages the other end as it is supported bythe bracket. The primary support is secured to the bracket 248. Ineither embodiment, the rollers 238, 239 ride along a pair of tracks 240,shown as curved rails or fenders, formed on the tilt control housing asthe chair is tilted rearwardly. As shown in the embodiment of FIGS. 20,41, 80 and 81, a pair of hook members 242 are mounted on the pivotmember and include downwardly extending hooks 244 that engage and slidealong a lip portion 246 of the tracks as the rollers 238 ride on thetracks. It should be understood that the tracks could take other forms,and could be formed for example and without limitation as slots in thecontrol housing side walls. Alternatively, the rollers or wheels can berotatably mounted to the housing, and the track can be formed on theseat support. Alternatively, the rollers can be omitted altogether, withthe respective members merely sliding relative to each other.

[0218] Referring to the embodiments of FIGS. 19 and 82, the bracket 248extends between and is secured to the side walls 234. The bracketincludes a pair of forwardly extending flange portions. A pair of guidemembers 252, configured as posts, are mounted to and extend laterallyoutward from the flange portions.

[0219] Referring to FIGS. 17-20 and 82, the primary seat support 202includes a rear portion 254 and a front portion 256, and opposite sides258. The auxiliary seat support 204 has a rear portion 260 pivotallymounted to the front portion 256 of the primary seat support 202 with apair of pivot members 262 extending laterally outward from the ends ofthe rim portion of the auxiliary seat support, which pivot members arereceived in laterally facing openings formed in the rim portion of theprimary seat support. Alternatively, a pair of tabs 271 on the primaryseat support are snap fitted in a pair of openings 273 formed on thesecondary seat support. The rim portion 232 includes an upper wall 266that engages a support wall 268 extending forwardly from the pivot axis270 on the primary seat support. In this way, the support wall 208supports the rear portion 260 of the auxiliary seat support and carriesthe load from the user.

[0220] A linkage assembly 272 is pivotally mounted to a forward portion262 of the auxiliary seat support. The linkage assembly includes a firstlink 274 having a first end 275 pivotally mounted to the auxiliary seatsupport with a pivot axle 276 at a first pivot axis. A second end of thefirst link is pivotally mounted to a second pivot link 278 at a secondpivot axis. In turn, the second link 278 is pivotally mounted to theseat support on the pivot member 236, 237 at the main pivot axis. In theembodiment of FIGS. 17-19 and 81, the first link 274 is preferablycurved and has a curved track 280, shown as a slot, formed therein.Alternatively, as shown in FIG. 20, the first link 274 can be linear.Referring to FIGS. 17-19 and 81, the track can be provided with abearing 282 or liner, which can further be formed as a cover 285 thatcovers the outer exposed surface of the link. The track 280, or bearing,is disposed on a first portion of the guide member 252, which rides inthe track. The first link 274 and track 280 preferably have a downwardlyopening concave curvature, or an upwardly facing convex curvature.

[0221] In operation, the user grips or grasps the front edge 262 of theauxiliary seat support and bends or flexes the auxiliary seat support asthe first link 274 moves relative to the guide 252 and as the first link274 pivots the second link 278 about the pivot member 236. The curvatureof the track 280 preferably corresponds to the distance between thepivot axes on the second link such that the linkage assembly does notbind up. The relative curvatures allow for the first link 274 tomaintain relatively the same orientation throughout the range of motionof the front portion of the seat. In addition, the first and secondlinks 274, 278, with the guide member 252 engaging the first link, actas a beam to carry the load from the front edge of the auxiliary seatsupport to the primary seat support. In one embodiment, shown in FIG.81, an upper surface of the link 274 is provided with a plurality ofindentations 279 that are indexed on a spring 277, so as to provide theuser with an indexed positioning device.

[0222] The seat also includes a lock device connected between theauxiliary seat support and the primary seat support. Of course, itshould be understood that in certain embodiments, for example where theseat is not slideably moveable relative to the housing, but rather onlypivotally moveable relative thereto, the lock device and the linkageassembly could be engaged with the housing, rather than the seatsupport.

[0223] Referring to FIGS. 18, 19 and 81, the lock device includes a pairof lock arms 284 joined with a handle portion pivotally connected to abracket 287 mounted to the auxiliary seat support on the pivot axle 276at a pivot axis. Each of the lock arms 284 includes a plurality ofnotches 288, forming a rack therealong, which selectively engage theouter portion of the guide member 252, configured as a latch member. Oneor more coil springs 294 is mounted on the axle and biases the arm intoengagement with the latch member. Of course, it should be understoodthat tension, compression, torsion springs, and other biasing deviceswould also work. Referring to the embodiment of FIGS. 18 and 19, thelock arm further includes a tab member 290 extending laterallytherefrom, which is received in an elongated opening or track 292 formedin the first link member 274. The tab member 290 rides in the opening292 and provides a limit on the range of motion of the lock arm.

[0224] Referring to the embodiment of FIGS. 81 and 82, the handle 286includes an arm that extends from the pivot axis 276 and includes apivot member 297 that is connected through a slotted opening 295 in theend of the lock arm 284. The opposite end of the lock arm is pivotallyconnected to the link member 278 and the link member 274.

[0225] In operation, the user lifts the handle 286 towards the frontedge 262 of the auxiliary seat support and rotates the handle relativeto the bracket 287 as he/she grips the front edge of the auxiliary seatsupport and thereby pivots the lock arm 284 against the force of thespring 294 to a disengaged position wherein the notches 288 aredisengaged from the latch member 252. The user then moves the front edge262 or portion of the auxiliary seat support to a desired positionrelative to the rear portion thereof by bending or flexing the auxiliaryseat support, and in particular the rim portion 232 thereof. In oneembodiment, the spring 277 indexes along the notches 279. When thedesired position is reached, the user releases the handle 286, such thatthe spring 294 biases the lock arm 284 into an engaged position, withone of the notches 288 engaging the latch member 252. It should beunderstood that the latch member can be formed on the lock arm, with thenotches or rack formed on the primary seat support or housing. The rackdefines four to five positions, although it should be understood thatthe seat can be bent or flexed between at least a first and secondposition, or to a plurality of such positions other than four or five.Preferably, the curvature of the upper surface of the forward portion ofthe seat support is greater and increases as it is bent or flexeddownwardly about a substantially horizontal axis, e.g., the pivot axis.Preferably, the seat supports are made of a resilient material, such asvarious polymeric or plastic, or elastomeric materials. In one preferredembodiment, the seat supports are made of nylon.

[0226] It should be understood that the primary and auxiliary seatsupports can be integrally formed as a single one-piece unit, with aforward portion of the seat support being bendable or flexible, orrelatively rigid, for example where no seat depth is intended. Likewise,it should be understood that the seat support can be formed as a singleone-piece web or sheet material, without an additional membrane, whereinthe one-piece web is made of a flexible material such as plastic andwherein the web forms the seating surface for the user. Of course, thesame linkage and lock mechanism can be used to control the flexing andpositioning of the forward portion of the seat support.

[0227] Referring to FIGS. 17-20 and 82, the auxiliary seat support 204preferably includes a plurality of laterally extending andlongitudinally spaced ribs 296 that form a recess 298. A pad 299 isdisposed in the recess 298 and provides support for the legs of theuser, especially as the forward portion of the seat is bent or flexeddownwardly, to form a waterfall contour of the front portion of theseat. In this way, the effective amount of seat support surfacecontacting the user's legs can be reduced, for example for shorterusers, simply by bending the forward portion of the seat. In addition,the user can lock or latch the forward portion in various positions,including at least the first and second position.

[0228] Referring to FIGS. 21 and 82, the rim portion 232 of the primaryand auxiliary seat supports includes a channel 233 and a plurality ofoutwardly extending hook members 235. A carrier member 237, shown inFIGS. 22 and 82, is secured around the periphery of a membrane 212. Themembrane is preferably a woven material, and can be made of variouscloth fabrics, elastomeric materials and yarns. For example, themembrane can be made from various materials described in U.S. Pat. No.6,059,368, which is hereby incorporated herein by reference.

[0229] The carrier member 237 has an insert portion 239 disposed in thechannel 233 and a cover portion 241 forming one or more recesses 243shaped to correspond to and mate with the hook members 235 of the rimportion. The insert portion 239 of the carrier member is disposed in thechannel 233 as the cover portion snaps over and engages the hookportions 235 so as to secure the membrane to the seat supports. Variousmethods of attaching a carrier member to a membrane, and for securingthe carrier member to the seat support, are disclosed in U.S. Pat. No.6,059,368, and U.S. patent application Ser. No. 09/666,624, entitledCarrier and Attachment Method for Load Bearing Fabric, filed Sep. 20,2000, the entire disclosures of which are hereby incorporated byreference.

[0230] An information card (not shown) providing indicia for using thevarious chair mechanisms can be slidably mounted to the seat support, oralternatively, to the armrests or backrest. Preferably, the card or thesupport structure therefore are provided with travel limiting members toprevent the card from being removed from the chair where it can be thenbe lost.

[0231] Tilt Assembly:

[0232] As shown in FIGS. 43, 46 and 51, the housing 10 includes a pivotbracket 32, a lower housing member 34 and an upper housing member 36.The pivot bracket 32 preferably has a substantially horizontal platform38 with an opening 40 formed therein and a raised rim 42 formed aroundthe opening, a pair of opposite side walls 44 having two pairs ofaligned openings 46 therethrough, and a rearwardly and downwardlyextending platform 39.

[0233] An annular bushing 50 has a first and second end 52, 54, with anannular flange 56 extending radially outward from the first end. Theannular bushing 50 is inserted through the opening 40 in the platform38, as the lower surface thereof abuts and is supported by the flange56. The bushing is mounted on the upper end of the support column 12.

[0234] The back support arms 310 are preferably secured to the pivotbracket 32 at the first openings 946 with a pair of insert pivot members317 as described above. In addition, a pair of assist springs 58 aremounted on the pivot members 317. Each spring 58 includes a first legengaging the pivot bracket 32 and a second leg engaging the back supportarm 310, wherein the spring biases the seat support in an upwarddirection. The springs 58 are preferably coil springs, although itshould be understood that torsion springs, tension springs andcompression springs also could be used to assist in the biasing of theback support member.

[0235] Referring to FIG. 51, a stop assembly 600 includes a stop block602 with an opening 604 therethrough. The stop block is disposed on theplatform 39, with the rim 42 received in a bottom end of the opening 604and with the bushing 50 extending through the opening in the stop block.The stop block includes a staircase 606 portion having a lower surface608 that abuts and is supported by the platform 39. The staircaseincludes a plurality of steps 610 formed on an upper portion thereof.The stop block 602 has a horizontal opening 612 formed therethrough. Anupside down U-shaped stop member 614 is pivotally mounted to the stopblock 602 with a pivot member 616. A spring 618 is mounted on the pivotmember 616 to bias the stop member 614 in a rear ward direction. Thestop member has a curved stop surface 620 formed on an underside of theapex of the member 614.

[0236] The lower housing member 34 has a bottom wall 60, having ahorizontal portion 62 and an upwardly and forwardly extending portion64, a pair of opposite side walls 66 and a front wall 68. The lowerhousing member further includes a mounting podium 70 extending upwardlyfrom a rear portion of the bottom wall. The podium 70 forms a cavitythat receives the stop block 602 and includes an opening 72 thatreceives the bushing 50. At least one of the side walls 66 includes aslot 74 formed therein through which various pivot members can extend.The front wall 68 includes a pair of horizontally extending slots 76,which are shaped to receive an end of the leaf springs 30.

[0237] Referring to FIG. 43, the upper housing member 36 has a bottomwall 78, a pair of side walls and a front wall. The front wall includesa pair of horizontally extending slots 84. The upper housing member isdisposed in the lower housing member 34 such that various fastener holesand slots 76, 84 are aligned, whereinafter the upper housing is securedto the lower housing with fasteners, or by welding and the like. Thelower surface of the bottom wall 78 of the upper housing member and theupper surface of the bottom wall 60 of the lower housing member arespaced apart, such that a linkage assembly can be disposed therebetween.

[0238] As shown in FIGS. 43 and 46, each support arm 310 also includes asecond opening positioned rearwardly of said first opening. The secondopening receives a support member 320, which defines a horizontal axis.

[0239] When the three-bar linkage formed by the back support, seat andhousing is combined with a pair of leaf springs 30, the resultant chaircan be designed in a compact and aesthetically pleasing form. It shouldbe understood that the three-bar linkage could be formed by pivotallyconnecting the seat support and back support to the housing and bypivotally and slideably connecting the seat support to the back support,or by pivotally connecting the seat support to the housing and to theback support and then pivotally and slideably connecting the backsupport to the housing.

[0240] In one preferred embodiment, shown in FIGS. 58-60 and 66-68, thehousing 910 includes a pair of pivot brackets 932, a lower or outerhousing member 934 and an upper or inner housing member 936. The pivotbrackets 932 are secured to opposite sides of the inner and outerhousing members with a plurality of fasteners. The pivot bracket 932define a pair of aligned openings 946 along a lateral horizontal axis.The back support arms 310 are preferably secured to the pivot bracket932 at the first openings 946 with a pair of insert pivot members 317 asdescribed above.

[0241] In this embodiment, the annular bushing 50 is disposed throughopenings 940, 972 in spaced apart portions of the inner and outerhousing members, with the bushing capturing those members. The bushingis mounted on the upper end of the support column 12. Referring to FIG.66, the lower housing member 934 has a bottom wall 960, a pair ofopposite side walls 966 and a front wall 968. The bottom wall includesthe opening 972 that receives the bushing 50. The side walls 966 includea plurality of openings 1002, 1004. Some of the openings 1002 areconfigured to receive fasteners, which join the lower housing member tothe upper member and pivot member. Other openings 1004 are shaped anddimensioned to receive various actuator members and controls.

[0242] Yet other openings 1006 are positioned to be connected to abackrest support, seat or other linkage assembly supporting a seatingstructure in a different seating arrangement, or to support variousactuator controls. In this way, the tilt housing is provided with aplurality of connector arrangements. For example, in one arrangement,the backrest support arms 402 and seat 200, which define a mountingarrangement, are configured to be pivotally connected to the pivotbrackets 932 at the opening 946 and pivotally and translatably supportedon the tracks 240 of the pivot bracket 932, with the opening 946 andtrack 240 defining a first connector arrangement. In another seatingarrangement, one or both of the seat 200 and the back support 304, whichdefine a mounting arrangement, which may be the same as or differentfrom the first mounting arrangement, is configured to be connected tothe upper and lower housing members at various openings, for exampleopenings 1006, which define a second connector arrangement. In otherseating arrangements, the seat and backrest are connected to the upperand lower housing, or a pivot bracket (which may vary from the disclosedpivot bracket) with a linkage assembly, which defines yet anothermounting arrangement. Indeed, various openings in the housing members,including one or more of the inner and outer housing members and pivotbracket, can be formed to define different connection points thatsupport the particular seating structure that is being mounted thereon.The connector and mounting arrangements can be sliding or fixed pivotsas required by the chair kinematics. The dies used to form the varioushousing members are preferably constructed so that additional connectoropenings can be added later if another pivot point is desired. Inaddition, if the pivot point falls outside the side surface of the upperor lower housing members 934, 936, the location can simply be providedby adding the side pivot brackets 932, as shown herein.

[0243] As explained above, the seat to back support pivot connection isnot defined by the tilt housing, and this connection, whether direct orby way of a link or linkage, can be made independent of theconfiguration of the tilt housing so as to further add to theflexibility of altering the kinematics of the seating structure.Moreover, a single back support can be used to support a variety ofdifferent configurations, simply by altering the shape and configurationof the armrests, which are connected to the seat as explained above.

[0244] Referring to FIGS. 60 and 67, the upper housing member 936 has abottom wall 978, a pair of side walls 980 and a front wall 982. Thefront 982 wall includes a pair of horizontally extending slots 84. Theupper housing member 936 is disposed in the lower housing member 934such that various fastener holes 1002 and connector openings 1004 arealigned, whereinafter the upper housing is secured to the lower housingwith fasteners, or by welding and the like. The lower surface of thebottom wall 978 of the upper housing member 936 and the upper surface ofthe bottom wall 960 of the lower housing member 934 are spaced apart atvarious locations.

[0245] Referring to FIG. 60, the back support 308 includes a web 1008having an upper and lower surface 1010, 1012 and a forwardly extendingedge 1014. The edge includes a raised central portion 1016 and a pair ofouter side portions 1018. The back support 308 further includes a pairof downwardly facing curved portions positioned 1020 on each side of themiddle portion.

[0246] Referring to FIGS. 58-60, a spring link 1022 includes a lower endhaving a pair of arms 1026 each with a rearwardly facing curved hookportion 1030 that pivotally engages the curved portions 1020 of the backsupport. In alternative embodiments, the spring link can be pivotallyconnected to the bask support with a pin or axle. An upper end of thespring link 1022 includes a forwardly facing hook portion 1024, which apair of tabs or locator members 1028 spaced therealong. A downwardlyfacing edge of the hook portion 1024 engages the top of the springs 30,with the tabs 1028 inserted in openings 33 in the springs to locate themrelative to the spring link. In operation, as the back support 308 tiltsrearwardly, the spring link 1022 pivots between the spring 30 and theback support 308, which avoids the spring sliding along the backsupport. Such sliding can create relatively large friction forces actingbetween the spring and back support. Of course it should be understoodthat the spring link can be omitted with the springs directly engagingthe back support.

[0247] Although the above-described three-bar mechanism is preferred, itshould be understood that the leaf springs can also be incorporated intosynchro-tilt chairs using linkage mechanisms such as four-bar linkagesand the like. With a four-bar linkage, links can be provided topivotally connect the seat support and/or back support to the housingand/or to each other about various horizontal axes.

[0248] As best shown in FIGS. 43-45, 47 and 60-62, a fulcrum member 90is moveably installed in the upper housing member 36 beneath the pair ofleaf springs 30. The fulcrum member 90 is preferably formed from asingle piece of hard, durable material having a relatively lowcoefficient of friction, such as DELRIN or CELCON Acetal, so as to allowthe fulcrum member to slide relatively easily along the bottom surfaceof the bottom wall 78, 978 of the upper housing, even when heavilyloaded by the spring. It should be understood, however, that othermaterials such as steel would also work. Similarly, the bottom surfacecan be lined with a material having a low coefficient of friction, suchas TEFLON, or the fulcrum member can be configured with rollers thatroll on the housing member.

[0249] The fulcrum member 90 includes a central portion 92, oppositeside support portions 94, each having a support surface 96, and a bottomsurface 97. Preferably, the support surfaces 96 are not symmetrical withrespect to any laterally extending vertical plane that is perpendicularto the longitudinal vertical plane in which the leaf springs 30 flex.Preferably, the support surface 96 is curvilinear and slopes rearwardlyand downwardly, such that a tangent of any point therealong slopesrearwardly and downwardly. Preferably, at least a portion, andpreferably the entirety, of the support surface 96 forms an arc. In apreferred embodiment, the arc has a radius between about 5 and 7 inches,and more preferably about 6 inches. In operation, the spring follows thesupport surface, which provides more contact therebetween as the usertilts rearwardly in the chair. In particular, as the spring bends in anarc, it naturally contacts the curved support surface of the fulcrum ata laterally extending tangent line. As the user reclines furtherrearwardly, the tangent contact moves rearwardly, thereby shortening thecantilevered length of the spring 30 at the end thereof engaging thesupport member 320 or spring link 1022. In turn, this change in thelength of the spring varies the stiffness of the spring as the usertilts rearwardly.

[0250] Referring to FIGS. 43-45 and 47, each support portion 94 has alaterally extending track 98, formed as a slot, in the bottom surfacethereof. The support portions 94 of the fulcrum member are supported byand slide along tracks formed on the upper surface of the bottom wall ofthe upper housing member. A rear lug 86 is formed on the rear portion ofthe bottom wall 78 and includes an opening 88 received on the annularbushing 50. The second end 54 of the bushing is then turned or rolled,or otherwise deformed, to form a second annular flange 57 extendingradially outward from the bushing. In this way, the bushing captures thepivot bracket 32, the stop block 602, and the upper and lower housingmembers 34, 36, or in an alternative embodiment the upper and lowerhousing members 934, 936.

[0251] Other embodiments of the fulcrum member and adjustment mechanismfor adjusting the longitudinal position thereof, are illustrated anddescribed in U.S. Pat. No. 6,250,715, which is hereby incorporatedherein by reference. It should be understood that the fulcrum member canalternatively be fixed within the housing at a specific location, suchthat the resistive force of the chair can not be adjusted.

[0252] Referring to FIGS. 43 and 48-50, in one preferred embodiment, anadjustment mechanism, including a linkage assembly 700 and an actuationmechanism 702, is connected to the fulcrum member 90. The linkageassembly 700 includes a cover bracket 704 mounted to a bottom wall 78 ofthe upper housing member 36. The cover bracket 704 includes a pair ofopposite arcuate tracks 706 centered around a opening 708 defining apivot axis. Preferably, the tracks, formed as slots in the bracket, aregenerally oriented in the lateral direction. The cover bracket 704further includes a pair of opposite side walls 710, to which a screwmember 712 is rotatably mounted. The bottom wall 78 of the upper housingmember also includes a pair of opposite arcuate tracks 714 centeredaround a pivot member 716, which extends downwardly from the bottom walland defines a pivot axis. Preferably, the tracks 714, which are formedas slots in the bracket, are generally oriented in the longitudinaldirection, or in a direction opposite the tracks 706 formed in the coverbracket.

[0253] The linkage assembly includes a first and second link 718, 720pivotally mounted to the cover bracket at the pivot axis. The first link718 has a first guide member 722 extending upwardly and verticallytherefrom and which is disposed in one of the tracks 714 in the upperhousing member. The first link 718 further includes a second guidemember 724 extending downwardly and vertically therefrom, and which isdisposed in one of the tracks 706 in the lower housing member. Thesecond link 720 has a first guide member 726 extending upwardly andvertically therefrom and which is disposed in the other track 714 in theupper housing member opposite the first track. The second link 720further includes a second guide member 728 extending downwardly andvertically therefrom, and which is disposed in the other track 706 inthe lower housing member. The first guide members 722, 726 of the linksare further inserted or disposed in the slots 98 formed in the bottom ofthe fulcrum member. The second guide members 724, 728 are disposed orinserted in a pair of longitudinally extending tracks 730 formed in anactuator member, which is threadably engaged with the actuation screw712, which is preferably, but not necessarily, double threaded. Thevarious guide members 722, 724, 726, 728 define pivot axes between thelinks 718, 720 and the fulcrum member 90 and the actuator member 732.

[0254] In operation, the user rotates a knob 734, or grippable member,secured to the end of the screw 712. Preferably, the knob is visible tothe user sitting in the chair and is located at approximately thehandfall position of the user's right hand when seated in the chair. Theknob is preferably circular and is shaped and dimensioned to be grippedin the palm of the user. In addition, the knob includes flexible finregions spaced around the circumference thereof that can be gripped bythe user's fingers. Preferably, the knob is rotated clockwise toincrease the biasing force of the springs, and counterclockwise todecrease the force. Preferably, as the screw 712 is rotated, itthreadably engages the actuator member 732 and moves it in a lateraldirection. As the actuator member 732 is moved laterally, it moves theguide members 724, 728 in the arcuate tracks 706, as the guide membersalso move in the tracks 730 formed in the actuator member. Movement ofthe guide members 724, 728 causes the first and second links 718, 720 topivot about the pivot axis 716, and thereby causes the guide members722, 726 to move within the arcuate tracks 714 formed in the upperhousing member. As the guide members 722, 726 move in the tracks 714,they engage the fulcrum member 90 and thereby move the fulcrum member inthe longitudinal direction as the guide members 722, 724 move in thetracks 98 formed in the fulcrum member. Preferably, the torque requiredto adjust the position of the fulcrum member is less than about 5 lbf.In addition, preferably the fulcrum can be moved from its maximum tominimum biasing position with a maximum of 6 full revolutions of theknob. It should be understood that the various interfacing tracks andguide members can be formed or mounted on the opposite members asdescribed herein without departing from the scope of this invention.

[0255] In alternative embodiment of the actuation mechanism, shown inFIGS. 60, 61, 69 and 70, a lead nut 1040 is threadably engaged on athreaded drive shaft, or lead screw 1042. The lead nut 1040 is disposedin a recess 1046 and captured by the middle portion 92 of the fulcrummember 90. As the drive shaft 1042 is rotated, it moves the lead nut1040 and the fulcrum 90 to the desired position. Preferably, the driveshaft 1042 includes an end shaft portion 1044 that is rotatablysupported at an opening 1050 formed between two gear housing members1048, which are joined to form a gear housing. A bevel gear 1052 is alsomounted on the drive shaft 1042, and is disposed in the gear housing.The bevel gear 1052 meshes with the bevel gear 810, which is mounted inthe gear housing about an axis 1054 substantially perpendicular to thelongitudinal axis of the drive shaft 1042. A bearing 1056 is disposedbetween the gear housing 1048 and the bevel gear 10. An actuation shaft1058 extends through the pivot member 804 and tube 22 and includes afirst end 1060 shaped and configured to non-rotatably mate with thebevel gear 810. An opposite second end of the shaft is connected to theknob 734.

[0256] In operation, the user rotates the knob 734, which rotates theshaft 1058 and the bevel gear 810. The bevel gear 810 meshes with androtates the bevel gear 1052 and thereby rotates the drive shaft 1042,which in turn moves the lead nut 1040 and fulcrum 90.

[0257] As best shown in FIG. 70, the gear housing preferably includes alocator portion 1064 formed along the bottom thereof that is disposed inan opening 1068 formed in the bottom of the upper, inner housing member936. The locator portion 1064 abuts the housing member 936 and preventsthe gear housing 1048 from moving in the fore/aft direction, and also inthe lateral direction. The gear housing 1048 further includes a locatorportion 1066 formed on the front thereof that slides under a shoulder1070 formed in the inner housing member 936. The locator portion abuts1066 the shoulder 1070 and prevents the gear housing 1048 from rotationabout the horizontal axis 1054 defined by the actuator shaft 1058.During assembly, the locator portion 1066 is first inserted under theshoulder 1070, and the gear housing 1048 is thereafter rotated such thatthe locator portion 1064 is disposed in the opening 1068. The springs30, once installed, further prevent the gear housing 1048 from beingdisplaced by applying a downward force to the gear housing 1048 by wayof the fulcrum member 90 and drive shaft 1042.

[0258] In an alternative embodiment, the drive shaft can simply extendthrough the front wall of the housing, to which it is rotatably mounted.An adjustment knob can be secured to the drive shaft. In operation,rotation of the drive shaft threadably engages and moves the fulcrummember.

[0259] The slotted openings 74, 86, 986 formed in the front walls 68,82, 982 of the housing members 34, 36, 936 defined cross members 83, 85.The pair of leaf springs 30 are installed in the chair by inserting anend 31 of each spring through one of the openings 74, 86, 986 such thata top surface of the spring 30 engages the cross member 83, 85. A tabmember 87, 987 or protuberance extends downwardly from the cross memberand is disposed in an opening 33 formed in the end of the spring tolocate and restrain the movement of the spring in the longitudinaldirection. Instead of a cross member formed integrally into the housing,a separate horizontal rod can be installed laterally in a forwardportion of the housing so as to engage the top surface of the forwardend of the spring.

[0260] The leaf springs 30 are constrained laterally within the housingby the sides of the center portion 92 of the fulcrum. The leaf springs30 extend rearwardly within the housing 10 such that a bottom surface ofthe springs engages the support surface 96 of the fulcrum member 90. Anend of the spring is inserted beneath the support member 320 or the edgeof the spring link hook portion 1024 such that top surface engagessupport member 320, which preferably includes a bearing member 321, orspring link 1022. Although each spring 30 is shown as a single leaf, itshould also be understood that multi-leaf springs could also beemployed. The leaf springs are preferably made of a composite material,such as a fiberglass and epoxy matrix, although it should be understoodthat other resilient materials such as steel would also work. Thecomposite material can be a fibrous composite, a laminated composite ora particulate composite. A suitable composite spring is commerciallyavailable from Gordon Plastics, Inc. of Montrose, Colo. under thespecification designation of GP68-UD Unidirectional Fiber Reinforced BarStock, and sold under the tradename POWER-TUFF. The fiberglass/epoxymatrix bar preferably is unidirectional with a glass content of about68% and a laminate density of 0.068 lbs./in.³. The bar preferably has aflexstrength of about 135,000 psi, a flex modulus of about 5,000,000psi, and an ultimate strain of about 2.4%. The use of a compositematerial bar can help eliminate the problems associated with creep.Another suitable spring is unidirectional fiberglass 70±2% by weight 30%vinyl esther hi-performance resin. The shape, size (width, thickness,length) and material of the springs can be varied to provide variousspring characteristics. In addition, the spring can be compressionmolded in various curved shapes to provide unique tilt balance and rideoptions.

[0261] In operation, the end 84 of the leaf spring 30 biases the supportmember 320, the back support 304 and the seat support 202, via the backsupport and armrests, in an upward direction so as to thereby support auser sitting in the chair. The opposite end of the spring engages thecross member 83, 85 or rod mounted in the housing, while an intermediateportion of the spring is supported by the fulcrum member 90. In thisway, the spring 30 acts as a simply supported beam with a load impartedintermediate the supported ends thereof. To adjust the force applied tothe back support, the user simply actuates the linkage assembly whichmoves the fulcrum member in a linear, longitudinal direction within thehousing. It should be understood that the spring biases the seat supportby way of the back support, and that in alternative embodiments, thespring can bias the back support and seat support through a commonelement, such as with a pivot member that pivotally connects thosemembers, or can directly bias the seat support and also the backsupport. In any of these embodiments, it should be understood that thesprings are biasing each of the seat support and back support,individually and in combination.

[0262] As the fulcrum member 90 is moved rearwardly in the housing 10,the distance between the point of support at the front of the housingand the support member is decreased, so as to correspondingly increasethe force applied by the rear end of the spring. Conversely, the fulcrummember 90 can be moved forwardly in the housing 10 to decrease theamount of resistive force applied to the seat support and back supportby increasing the beam length, or the distance between the fulcrum 90and the support member 320 or spring link 1022. Since the leaf spring 30is simply supported at each end, rather being clamped to the housing,the pivot rod (or spring link) or both, bending moments are notintroduced at the ends of the spring. When clamped, the properties ofthe spring, and the amount of the clamping, can effect the loading andassociated stresses. Moreover, by providing a simply supported spring,tolerances can be relaxed and the curvature of the spring is allowed toundulate as the beam length changes.

[0263] Because the leaf springs 30 are disposed in the housing 10 in aside-by-side arrangement, and are preferably formed as flat bars, thehousing can be made more compact at lower cost in an aestheticallypleasing way. This advantage is even more apparent when the leaf springarrangement is combined with the three bar mechanism. Moreover, theresistive force of the spring can be adjusted easily and simply byslideably moving the fulcrum 90 within the housing 10. Since theresistive force is determined by the beam length, rather than byprestressing the spring, the adjustment does not require a progressivelylarger actuation force as is typically associated with torsion springsand bars and compression springs.

[0264] Tilt Limiter:

[0265] Referring to FIGS. 52-57, one preferred tilt limiter mechanism isshown. Although the tilt limiter is shown as having a mechanism securedto the back support, with the stop members 602, 614 mounted to thehousing, or base, it should be understood that the location of thoseaspect could be reversed, or alternatively, could be operative between aseat support and a housing, or base.

[0266] In a preferred embodiment, the tilt limiter mechanism includes aU-shaped bracket 622 having a rear wall 624, a pair of side walls 626and a pair of mounting flanges 628 secured to the back support. Itshould be understood that the bracket could be formed integrally withthe back support. The tilt limiter includes an upper and lower tiltlimiter member 630, 632 slideably mounted to the back support on a guidemember 634 that extends through a slot 636 formed in the back supportand has an upper and lower guide portion 638, 640 extending upwardly anddownwardly from the support member respectively. In particular, eachtilt limiter member includes a track 642, 644 disposed on one of theguide portions.

[0267] The upper tilt limiter member 630 includes a upwardly facing stopsurface 646, which is provided with a curved contour to mate with thelower surface 620 of the stop member 614 when the upper tilt limitermember is moved forwardly under the stop member 614. In this way, theupper tilt limiter member 630 limits the forward tilt of the backsupport and attached seat as it engages the stop member 614. Inoperation, the tilt limiter member 630 is slid rearwardly such that theback support 304 can pivot forwardly until a curved lip 648 formed on aleading edge of a back support cross member that extends between the armportions 310 engages the stop member 614 to define a forward tiltposition, as shown in FIG. 55. In this position, the lower tilt limitermember 632 can be moved forwardly to engage an uppermost step 650 on thestop block, such that the backrest is locked in the forward tiltposition.

[0268] The backrest, and chair, can also be locked in a neutral, orupright position, as shown in FIG. 56, by engaging the upper stop 614with the upper tilt limiter member 630 and by engaging a next lower step652 from the uppermost step with the lower tilt limiter member 632.Other rear tilt positions can be limited by moving the lower tiltlimiter member 632 to various positions such that it selectively engagesone of the next lower steps 610 on the stop member 602. Preferably, thesteps are arranged and dimensioned to provide tilt limit positions at 5degree tilt intervals.

[0269] Each tilt limiter member 630, 632 is moved in the longitudinaldirection using an actuator mechanism. The actuator mechanism includes apair of drive links 654 mounted to a first and second coaxially mountedpivot members 658, 660, each having a grippable portion, or paddlemounted to an end thereof. The shape of the paddles are configured toresemble the shape of the overall chair, as shown in FIG. 53. Inparticular, the position of the upstanding paddle, which is preferablyused to adjust the position of the rear tilt limiter, provides indiciato the user about the setting of the tilt limiter and the maximum reartilt position thereof, even when the chair is not in such a position.Likewise, the substantially horizontal paddle, which is preferably usedto adjust the position of the forward tilt limiter, provides indicia tothe user about the setting of the forward tilt limiter, even when thechair is not in such a position. The pivot members 658, 660 arerotatably mounted to the bracket about a horizontal axis of rotation. Itshould be understood that the drive links and pivot members can bemounted about spaced apart, and even non-parallel, axes of rotation.

[0270] A pair of follower links 656 each have a first end are pivotallymounted to the bracket 624 at a first and second pivot axis 666, 668,which are spaced from the horizontal axis of rotation, and which arepreferably, but not necessarily coaxial. A second end of the followerlinks 656 are each pivotally mounted to a coupling link 672, which isfurther pivotally mounted to the tilt limiter members 630, 632. Itshould be understood that the follower links can be directly coupled tothe tilt limiter members without an intervening or intermediate couplinglink.

[0271] A pair of springs 674 are mounted on the pivot member about theaxis. Each spring includes a first arm 676 engaging a lug on one of thedrive links 654 and a second arm 678 engaging a lug on one of thefollower links 656. A pair of indexing members 680, formed as cantileversprings are mounted to the rear wall 624 of the bracket 622 andselectively engage racks 682 formed on the drive members 654.

[0272] In operation, the user rotates one of the levers 662, 664 to adesired tilt limiter position determined by the indexing member 680,which in turn pivots a corresponding drive link 654 and an associatedarm 676 of the spring 674. If there is no load on the seat and backrestcreating a frictional force between the tilt limiter member 630, 632 andthe stop member 602, 614, the other arm of the spring 678 moves thefollower link 656, coupling link 672 and the connected tilt limitermember 630, 632 to the desired position. However, if a load is appliedto create a friction force between the tilt limiter member 630, 632 andthe stop member 614, 606, the spring 674 will simply load up, but willnot move the tilt limiter member until the user removes the load,wherein the spring 674 moves the tilt limiter to the selected position.In this way, the user is provided with pressure release mechanisms forboth the forward and rear tilt limiters. The various drive and followerlinks can be made of metal or plastic, or other suitable materials knowto those of skill in the art.

[0273] In an alternative preferred embodiment, best shown in FIGS. 60and 63-65, tilt limiter members 1080, 1082 are pivotally mounted to thetilt housing, and in particular the outer housing 934, and releasablyengage the back support member 308. In particular, a forward tiltlimiter member 1080 includes a base portion 1084 pivotally mounted abouta substantially horizontal axis between a pair of rearwardly facing lugs1086 formed on the upper housing member 936. The tilt limiter member1080 is mounted on a pivot axle 1088 about a pivot axis 1098, althoughit should be understood that such an axle could be formed integrallywith the tilt limiter member. The tilt limiter member includes 1080 astop arm 1090 extending outwardly, radially from the base portion 1084.The tilt limiter member 1080 further includes a pair of limiter armmembers 1092 extending from the base portion and defining a space 1094therebetween. The tilt limiter member 1080 further includes a pivot axisopening 1098 spaced apart from the axis in a substantially parallelrelationship therewith. Finally, the tilt limiter member includes anotch 1100 or groove formed on one of the tilt limiter arms 1092opposite the other of the arms.

[0274] In operation, the tilt limiter member 1080 is rotated between aforward tilt position, wherein the stop arm 1090 is pivoted such that itextends over the central portion 1016 of the back support web edge 1014and engages the top surface of the web 1010, and a normal operatingposition, wherein the stop arm 1090 is pivoted downwardly such that thecentral portion 1016 of the back support engages the base portion 1084of the tilt limiter member 1080. The rearwardly facing edge 1102 of theupper housing member 936 is disposed in the space 1094 between the tiltlimiting arms 1092, which define and limit the rotation of the tiltlimiter member between the normal and forward tilt positions. Inaddition, an over-center spring 1104 is mounted to the upper housingmember and engages the notch 1100, and biases the tilt limiter member toone or the other of the normal and forward tilt positions.

[0275] Referring to FIGS. 60 and 63, the rearward tilt limiter member1082 includes a pair of spaced apart stop members 1106 connected with aU-shaped connector 1108 or bridge. The tilt limiter member 1082 ispivotally mounted to the lower housing member 936 about a pivot axis1110. In one preferred embodiment, the stop members 1106 each have aninwardly extending pivot member 1112 that are pivotally disposed in apair of openings 1114 formed on side walls of a center portion 1116 ofthe upper housing. A pivot member, axially aligned with the pivotmembers 1112, is further secured through the outer side wall 966 of thelower housing member and pivotally engages an opening 1118 in theopposite outer sides of the stop members. The pivot members can also beintegrally formed with the tilt limiter member. To install the tiltlimiter member 1082, the connector 1108 is flexed such that the pivotmembers 1112 can be snapped into engagement with the housing member 934.The outer pivot members can then be installed to pivotally connect thetilt limiter member 1082 to the housing member 936. The tilt limitermember 1082 further includes an opening 1120 spaced apart from the pivotaxis 1110. In addition, the tilt limiter member 1082 has a rack 1122, ora plurality of indexing notches, formed along an outer side portion ofthe stop members. A detent 1124, such as a spring, is selectivelyengaged with one or more of the indexing notches 1122 as the tiltlimiter member 1082 is pivoted between various rear tilt positions.

[0276] Each stop member 1106 has a stepped profile or contour defining aplurality of steps 1126 and corresponding stop surfaces. In addition,the bottom surface 1128 of the stop member is curved and engages thebottom wall 960 of the housing member 934, which is shaped to supportthe bottom surface. In this way, the loads applied to the stop members1106 by the back support 308 are carried by the housing member 934,rather than the pivot members 1112.

[0277] In operation, the tilt limiter member 1082 is pivoted between aplurality of tilt limiter positions, wherein the back support sideportions 1018 engage one of the steps 1126 of the tilt limiter. In oneembodiment, the tilt limiter member has four positions, although otherpluralities of steps and positions are suitable.

[0278] Referring to FIGS. 60 and 63-65, each tilt limiter member isrotated about a respective pivot axis using an actuator mechanismsimilar to that described above. The actuator mechanism includes a pairof drive links 1654 matingly engaged with and mounted to a first andsecond coaxially mounted pivot members 1658, 1660, each having agrippable portion, or paddle mounted to an end thereof, with the paddlesarranged and configured as described above. The drive links 1654preferably each include a tubular pivot portion 1662 and an arm 1664extending laterally therefrom. The arm 1664 includes an opening 1666formed in an end portion thereof. The first drive link 1654 is insertedthrough and pivotally engaged with the opening 1006 in one of the sidewalls 966 of the housing member 934, with the arm 1666 positioned insidethe housing. The drive link 1654 includes an annular flange 1668 thatengages the outer surface of the housing side wall 966 and prevents thedrive link from being pulled through the opening 1006. In oneembodiment, wherein the seating structure is configured without a tiltlimiter, the drive link 1654 is disabled simply by inserting a fastenerthrough an opening 1670 formed in the annular flange and securing thedrive link to the housing in a non-rotatable relationship. A drive shaft1672 connected to a paddle is inserted into the drive link 1654. Thedrive shaft 1672 includes a circumferential groove 1674 that engages thedrive link 1654 with a snap fit. On the opposite side of the housing, asecond drive link 1654 is inserted through the opening 1006, with anannular flange engaging the outer surface of the side wall 966 and withthe arm 1664 disposed inside the housing. The drive shaft 1672 extendsthrough the pivot member 1658 and the near drive link 1654 and capturesthe near drive link 1654 and pivot member 1658 and secures them to thehousing as the drive shaft 1672 is snap fitted with the drive link 1654on the opposite side.

[0279] The pivot members 1658, 1660 are rotatably mounted to the housingabout a horizontal axis of rotation. It should be understood that thedrive links 1654 and pivot members 1658, 1660 can be mounted aboutspaced apart, and even non-parallel, axes of rotation.

[0280] A first follower link 1700 has a first end pivotally mounted tothe drive link 1654 at a first pivot axis. A second end of the followerlink is pivotally mounted to the forward tilt limiter member 1080 at theopening 1096. A second follower link 1702 has a first end pivotallymounted to the drive link 1654 at a first pivot axis. A second end ofthe follower link 1702 is pivotally mounted to the rear tilt limitermember at the opening 1120.

[0281] In operation, the user rotates the rearward or forward pivotmember 1658, 1660, for example by gripping a paddle member 1802, 1804.As the pivot member 1658, 1660 is rotated, the drive link 1654 ispivoted, which in turn moves the follower link 1700, 1702 and thecorresponding tilt limiter member 1080, 1082 to the desired position. Apair of triangular shaped arm members 1083 formed on the tilt limitermember 1082 hold the ends of the follower links in engagement therewith.

[0282] As shown in FIGS. 58 and 60, the paddle members 1802, 1804, oractuators, are pivotable about the same axis. Preferably, the paddlemember 1802, which controls the forward tilt limiter, is oriented ingenerally the same orientation as the seat, e.g., in a generallyhorizontal orientation, while the paddle member 1804, which controls therear tilt limiter or the tilt of the back and back, is oriented ingenerally the same orientation as the back. In addition, the paddlemembers are arranged adjacent one another in generally the samerelationship as the seat and back. In addition, the paddle member 1804is generally shaped like the back member. In this way, the paddlemembers 1802, 1804 provide indicia and are intuitive to the user forcontrol of the rear tilt and forward tilt. Of course, the paddlemembers, and their orientation and shape, could be suitable forcontrolling other adjustment mechanisms, and preferably adjustmentmechanisms associated with the seat and back respectively.

[0283] Various aspects of the seating structure are also disclosed inU.S. Provisional Application No. 60/356,478, filed Feb. 13, 2002, andU.S. Provisional Application No. 60/418,483, filed Oct. 15, 2002, thesame day as the present application and entitled “Backrest For A SeatingStructure With An Adjustable Sacral Support,” both of which are herebyincorporated herein by reference.

[0284] Although the present invention has been described with referenceto preferred embodiments, those skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. As such, it is intended that the foregoingdetailed description be regarded as illustrative rather than limitingand that it is the appended claims, including all equivalents thereof,which are intended to define the scope of the invention.

What is claimed is:
 1. An armrest assembly for a seating structurecomprising: a support member comprising an upwardly extending curvedspine portion having a first defined curvature; a stem slidably disposedon said support member and comprising a curved portion having a seconddefined curvature corresponding to and mating with said first curvatureof said spine portion, wherein said curved portion of said stem isslideably mated with said curved portion of said spine portion; anarmrest supported by said stem; and a latch mechanism moveable betweenat least an engaged position and a disengaged position, wherein saidlatch mechanism engages at least one of said stem and said supportmember to prevent movement therebetween when in said engaged position,and wherein stem is moveable relative to said support member when saidlatch mechanism is in the disengaged position.
 2. The invention of claim1 wherein one of said stem and said spine portion comprise a rack andwherein the latch mechanism is connected to the other of said stem andsaid spine portion, wherein said latch mechanism comprises a leverpivotably mounted to said other of said stem and said spine portion,said lever pivotable between said engaged and disengaged positions,wherein said lever comprises an engagement portion, wherein saidengagement portion is engaged with said rack when said lever is in theengaged position, and wherein said engagement portion is disengaged fromsaid rack when said lever is in the disengaged position.
 3. Theinvention of claim 2 wherein said rack is disposed on said spine portionand said lever is pivotably mounted to said stem.
 4. The invention ofclaim 3 wherein said rack comprises a sleeve mounted on said spineportion.
 5. The invention of claim 1 further comprising an index memberselectively engaging said at least one of said stem and said supportmember when said latch mechanism is in the disengaged position.
 6. Amethod of adjusting the position of an armrest comprising: providing asupport member comprising an upwardly extending curved spine portionhaving a first defined curvature, and a stem slidably disposed on saidsupport member and comprising a curved portion having a second definedcurvature corresponding to and mating with said first curvature of saidspine portion, an armrest supported by said stem, and a latch mechanismmoveable between at least an engaged position and a disengaged position,wherein said latch mechanism engages at least one of said stem and saidsupport member to prevent movement therebetween when in said engagedposition; moving said latch mechanism to said disengaged position;sliding said curved portion of said stem relative to said curved spineportion while said latch mechanism is in said disengaged position; andmoving said latch mechanism to said engaged position.
 7. The inventionof claim 6 wherein one of said stem and said spine portion comprise arack and wherein the latch mechanism is connected to the other of saidstem and said spine portion, wherein said latch mechanism comprises alever pivotably mounted to said other of said stem and said spineportion, wherein said lever comprises an engagement portion, whereinsaid engagement portion is engaged with said rack when said lever is inthe engaged position, and wherein said moving said latch mechanism tosaid disengaged position comprises pivoting said lever and therebydisengaging said engagement portion from said rack, and wherein saidmoving said latch mechanism to said engaged position comprises pivotingsaid lever and thereby engaging said engagement portion with said rack.8. The invention of claim 7 wherein said rack is disposed on said spineportion and said lever is pivotably mounted to said stem.
 9. Theinvention of claim 8 wherein said rack comprises a sleeve mounted onsaid spine portion.
 10. The invention of claim 6 further comprising anindex member selectively engaging said at least one of said stem andsaid support member when said latch mechanism is in the disengagedposition.
 11. An armrest assembly for a seating structure comprising: asupport member; a stem slidably disposed on said support member andmoveable relative to said support member; an armrest supported by saidstem; a latch mechanism moveable between at least an engaged positionand a disengaged position, wherein said latch mechanism engages at leastone of said stem and said support member to prevent movementtherebetween when in said engaged position, and wherein said stem ismoveable relative to said support member when said latch mechanism is inthe disengaged position; and an index member selectively engaging atleast one of said support member and said stem when said latch mechanismis in the disengaged position as said stem is moved relative to saidsupport member.
 12. The invention of claim 11 wherein said at least oneof said support member and said stem comprises a plurality of notches,wherein said index member successively, selectively engages at least oneof said plurality of notches as said stem is moved relative to saidsupport member.
 13. The invention of claim 12 wherein one of said stemand said support member comprise a rack and wherein the latch mechanismis connected to the other of said stem and said support member, whereinsaid latch mechanism comprises a lever pivotably mounted to said otherof said stem and said support member about a pivot axis, said leverpivotable between said engaged and disengaged positions, wherein saidlever comprises an engagement portion, wherein said engagement portionis engaged with said rack when said lever is in the engaged position,and wherein said engagement portion is disengaged from said rack whensaid lever is in the disengaged position, and wherein said index memberis pivotably mounted on said pivot axis. 14 The invention of claim 13wherein said index member further comprises a bumper portion, whereinsaid bumper portion is engaged with said one of said stem and saidsupport member when said lever is in the engaged position, and whereinsaid bumper portion is disengaged with said one of said stem and saidsupport member when said lever is in the disengaged position.
 15. Theinvention of claim 13 wherein said rack is disposed on said supportmember and said lever and said index member are pivotably mounted tosaid stem.
 16. The invention of claim 15 wherein said rack comprises asleeve mounted on said support member, and wherein said sleeve furthercomprises said plurality of notches.
 17. A method of adjusting theposition of an armrest comprising: providing a support member, a stemslidably disposed on said support member, an armrest supported by saidstem, a latch mechanism moveable between at least an engaged positionand a disengaged position, wherein said latch mechanism engages at leastone of said stem and said support member to prevent movementtherebetween when in said engaged position, and wherein stem is moveablerelative to said support member when said latch mechanism is in thedisengaged position, and an index member selectively engaging at leastone of said support member and said stem when said latch mechanism is inthe disengaged position; moving said latch mechanism to said disengagedposition; sliding said stem relative to said support member while saidlatch mechanism is in said disengaged position; and selectively engagingsaid at least one of said support member and said stem with said indexmember as said stem is slid relative to said support member.
 18. Theinvention of claim 17 wherein said at least one of said support memberand said stem comprises a plurality of notches, and wherein saidselectively engaging said at least one of said support member and saidstem comprises successively, selectively engaging at least one of saidplurality of notches with said index member as said stem is movedrelative to said support member.
 19. The invention of claim 18 whereinone of said stem and said support member comprise a rack and wherein thelatch mechanism is connected to the other of said stem and said supportmember, wherein said latch mechanism comprises a lever pivotably mountedto said other of said stem and said support member, wherein said levercomprises an engagement portion, wherein said engagement portion isengaged with said rack when said lever is in the engaged position, andwherein said moving said latch mechanism to said disengaged positioncomprises pivoting said lever to said disengaged position and therebydisengaging said engagement portion from said rack, and wherein saidindex member is pivotably mounted on said pivot axis, and furthercomprising pivoting said index member from a nonindexing position to anindexing position as said lever is pivoted to said disengaged position.20. The invention of claim 19 wherein said index member furthercomprises a bumper portion, wherein said bumper portion is engaged withsaid one of said stem and said support member when said lever is in theengaged position, and wherein said bumper portion is disengaged withsaid one of said stem and said support member when said lever is in thedisengaged position, and wherein said pivoting said index member fromsaid nonindexing position to said indexing position comprises pivotingsaid bumper portion from an engaged position to a disengaged position.21. The invention of claim 19 wherein said rack is disposed on saidsupport member and said lever and said index member are pivotablymounted to said stem.
 22. The invention of claim 21 wherein said rackcomprises a sleeve mounted on said support member, and wherein saidsleeve further comprises said plurality of notches.
 23. An armrestassembly comprising: a platform; an armrest support moveably supportedon said platform, wherein said armrest support is moveable relative tosaid platform between at least a first position and a second position; alinear gear disposed on one of said platform and said armrest supportand extending in a substantially horizontal direction; a pinion gearrotatably mounted on the other of said platform and said armrest supportabout a substantially vertical rotation axis, wherein said pinion gearmeshes with said linear gear as said armrest support is moved relativeto said platform between said at least said first and second positions.24. The invention of claim 23 wherein said linear gear comprises firstand second linear gears disposed on said one of said platform and saidarmrest support, wherein said first and second linear gears are spacedapart in a parallel relationship, and wherein said pinion gear comprisesa first and second pinion gear mounted on said other of said platformand said armrest support about spaced apart and parallel first andsecond substantially vertical rotation axes, wherein said first piniongear meshes with said first linear gear and with said second piniongear, and wherein said second pinion gear meshes with said second lineargear and said first pinion gear as said armrest support is movedrelative to said platform between said at least said first and secondpositions.
 25. The invention of claim 23 further comprising at least oneguide member extending from one of said platform and said supportmember, and a track formed in the other of said platform and saidarmrest support, wherein said guide member moves within said track assaid armrest support is moved relative to said platform between said atleast said first and second positions.
 26. The invention of claim 25wherein said at least one guide member comprises a first and secondguide member extending from said one of said platform and said supportmember in a spaced apart relationship, and wherein said at least onetrack comprises a first and second track formed in the other of saidplatform and said armrest support in a spaced apart relationship. 27.The invention of claim 23 further comprising a pawl member moveablymounted on one of said platform and said armrest support, wherein saidpawl is moveable between an engaged position, wherein said pawl engagessaid pinion gear and whereby said pinion gear is prevented from rotatingand a disengaged position wherein said pawl is disengaged from saidpinion whereby said pinion gear is allowed to rotate.
 28. The inventionof claim 27 further comprising a spring biasing said pawl into saidengaged position.
 29. The invention of claim 23 wherein said platformcomprises a first platform and further comprising a second platformdisposed adjacent said first platform, wherein one of said first andsecond platforms comprises a protuberance, and the other of said firstand second platforms comprises a plurality of recesses shaped toreceived said protuberance, and wherein said first platform is pivotallymounted to said second platform about a substantially vertical pivotaxis spaced from said protuberance, wherein said first platform ispivotable relative to said second platform about said pivot axis betweena plurality of pivot positions corresponding to said plurality of saidrecesses.
 30. The invention of claim 29 wherein said first platformcomprises a first member joined to a second member, wherein said one ofsaid pinion gear and said linear gear are formed on said first member,and wherein said one of said protuberance and said plurality of recessesare formed on said second member.
 31. A method of adjusting the positionof an armrest comprising: providing a platform, an armrest supportmoveably supported on said platform and moveable between at least afirst position and a second position, a linear gear disposed on one ofsaid platform and said armrest support and extending in a substantiallyhorizontal direction, and a pinion gear rotatably mounted on the otherof said platform and said armrest support about a substantially verticalrotation axis; and moving said armrest support relative to said platformbetween said at least said first and second position, and therebymeshing said pinion gear with said linear gear.
 32. The invention ofclaim 30 wherein said linear gear comprises first and second lineargears disposed on said one of said platform and said armrest support,wherein said first and second linear gears are spaced apart in aparallel relationship, and wherein said pinion gear comprises a firstand second pinion gear mounted on said other of said platform and saidarmrest support about spaced apart and parallel first and secondsubstantially vertical rotation axes, and wherein said moving saidarmrest support relative to said platform between said at least saidfirst and second position comprises meshing said first pinion gear withsaid first linear gear and with said second pinion gear, and meshingsaid second pinion gear with said second linear gear and said firstpinion gear.
 33. The invention of claim 31 further comprising at leastone guide member extending from one of said platform and said supportmember, and a track formed in the other of said platform and saidarmrest support, and wherein said moving said armrest support relativeto said platform between said at least said first and second positioncomprises moving said guide member within said track.
 34. The inventionof claim 33 wherein said at least one guide member comprises a first andsecond guide member extending from said one of said platform and saidsupport member in a spaced apart relationship, and wherein said at leastone track comprises a first and second track formed in the other of saidplatform and said armrest support in a spaced apart relationship andwherein said moving said guide member within said track comprises movingsaid first and second guide members within said first and second tracksrespectively.
 35. The invention of claim 31 further comprising providinga pawl member moveably mounted on one of said platform and said armrestsupport and moving said pawl between an engaged position, wherein saidpawl engages said pinion gear whereby said pinion gear is prevented fromrotating, and a disengaged position, wherein said pawl is disengagedfrom said pinion whereby said pinion gear is allowed to rotate.
 36. Theinvention of claim 35 further comprising a spring biasing said pawl intosaid engaged position.
 37. The invention of claim 31 wherein saidplatform comprises a first platform and further comprising a secondplatform disposed adjacent said first platform, wherein one of saidfirst and second platforms comprises a protuberance, and the other ofsaid first and second platforms comprises a plurality of recesses shapedto received said protuberance, and wherein said first platform ispivotally mounted to said second platform about a substantially verticalpivot axis spaced from said protuberance, and further comprisingpivoting said first platform relative to said second platform about saidpivot axis between a plurality of pivot positions corresponding to saidplurality of said recesses.
 38. A seating structure comprising: aprimary seat support having a rear portion and a front portion; and anauxiliary seat support having a rear portion and a front portion,wherein said rear portion of said auxiliary seat support is connected tosaid front portion of said primary seat support, said primary andauxiliary seat supports adapted to support the body of a user, whereinat least a portion of said auxiliary seat support is flexible, andwherein said front portion of said auxiliary seat support is moveablebetween at least a first and second position relative to said rearportion of said auxiliary seat support as said at least said flexibleportion of said auxiliary seat support is flexed.
 39. The invention ofclaim 38 wherein rear portion of said auxiliary seat support ispivotally connected to said front portion of said primary seat support.40. The invention of claim 38 further comprising a linkage assemblyconnecting said front portion of said auxiliary seat support and one ofsaid primary seat support and a housing, wherein said housing supportssaid primary seat support.
 41. The invention of claim 40 wherein saidlinkage assembly comprises a first link pivotally mounted to said frontportion of said auxiliary seat support at a first pivot axis andpivotally mounted to a second link at a second pivot axis spaced fromsaid first pivot axis, wherein said second link is pivotally mounted tosaid one of said primary seat support and said housing at a third pivotaxis spaced from said second pivot axis, wherein said second link ispivoted about said third pivot axis between at least a first and secondpivot position as said front portion of said auxiliary seat support ismoved between said at least said first and second position.
 42. Theinvention of claim 41 wherein said first link has a track formedtherein, and further comprising a guide member mounted to said one ofsaid primary seat support and said housing, wherein said guide member isdisposed in said track, wherein said first link moves relative to saidguide disposed in said track as said front portion of said auxiliaryseat support is moved between said at least said first and secondposition.
 43. The invention of claim 42 wherein said track is acurvilinear slot formed in said first link.
 44. The invention of claim41 further comprising a lock device comprising a lock arm pivotallymounted to said front portion of said auxiliary seat support at a fourthpivot axis, wherein said lock arm comprises a plurality of notchesshaped to releasably engage a latch member mounted on said one of saidprimary seat support and said housing.
 45. The invention of claim 44wherein said lock device further comprises a handle connected to saidlock arm, and a spring biasing said lock arm into engagement with saidlatch member.
 46. The invention of claim 38 wherein said auxiliary seatsupport comprises a rim portion and a plurality of laterally extendingand longitudinally spaced ribs forming a recess with said rim, andfurther comprising a pad received in said recess.
 47. The invention ofclaim 38 further comprising a one-piece, continuous flexible membranesecured to said primary and said auxiliary seat supports and defining aseat support surface adapted to contact the body of the user.
 48. Theinvention of claim 47 wherein said membrane comprises a carrier membersecured around at least a portion of a periphery of said membrane,wherein said carrier member is secured to said primary and auxiliaryseat supports.
 49. The invention of claim 40 further comprising a lockdevice releasably connected between said auxiliary seat support and saidat least said one of said primary seat support and said housing in aplurality of lock positions including at least a first and second lockposition corresponding to said at least said first and second positionof said front portion of said auxiliary seat support, wherein said lockdevice maintains said position of said front portion of said auxiliaryseat support when in one of said plurality of lock positions
 50. Amethod for adjusting the depth of a seating structure comprising:providing a primary seat support having a rear portion and a frontportion, and an auxiliary seat support having a rear portion and a frontportion, wherein said rear portion of said auxiliary seat support isconnected to said front portion of said primary seat support, wherein atleast a portion of said auxiliary seat support is flexible; and movingsaid front portion of said auxiliary seat support between at least afirst and second position relative to said rear portion of saidauxiliary seat support and thereby flexing said at least said flexibleportion of said auxiliary seat support.
 51. The invention of claim 50further comprising locking said auxiliary seat support in one of aplurality of positions, including at least said first and secondpositions.
 52. The invention of claim 50 further comprising providing alinkage assembly connecting said front portion of said auxiliary seatsupport and one of said primary seat support and a housing, wherein saidhousing supports said primary seat support, wherein said linkageassembly comprises a first link pivotally mounted to said front portionof said auxiliary seat support at a first pivot axis and pivotallymounted to a second link at a second pivot axis spaced from said firstpivot axis, wherein said second link is pivotally mounted to said one ofsaid primary seat support and said housing at a third pivot axis spacedfrom said second pivot axis, and wherein said moving said front portionof said auxiliary seat support between at least a first and secondposition relative to said rear portion of said auxiliary seat supportcomprises pivoting said second link about said third pivot axis betweenat least a first and second pivot position.
 53. The invention of claim52 wherein said first link has a track formed therein, and furthercomprising providing a guide member mounted to said one of said primaryseat support and said housing, wherein said guide member is disposed insaid track, and wherein said moving said front portion of said auxiliaryseat support between at least a first and second position relative tosaid rear portion of said auxiliary seat support comprises moving saidfirst link relative to said guide member as said guide member slides insaid track.
 54. A seating structure comprising: a seat supportcomprising a forward portion, a rear portion and opposite, laterallyspaced sides, wherein at least said forward portion is bendable about asubstantially horizontal and laterally extending axis between at least afirst and second position, wherein said forward portion has a greatercurvature when in said second position compared with said firstposition; and a lock device moveable between at least an engagedposition and a disengaged position, wherein said lock device maintainssaid seat support in one of said at least said first and secondpositions when in said engaged position, and wherein said seat supportis bendable between said at least said first and second positions whensaid lock device is in said disengaged position.
 55. The invention ofclaim 54 wherein said at least said forward portion that is bendabledefines an upper, convex support surface.
 56. A backrest for a seatstructure, the backrest comprising: a frame member; a compliant,resilient back member having a top, a bottom and opposite sides, whereinsaid back member is mounted to said frame member, said back membercomprising a lumbar region, a thoracic region disposed above said lumbarregion, and a lower region disposed below the lumbar region, whereinsaid lumbar region comprises a first array of openings formedtherethrough, said first array comprising a first plurality ofstaggered, elongated openings, wherein said first plurality of saidfirst array openings are elongated in a direction from the top to thebottom of the back member, and wherein said thoracic region comprises asecond array of openings formed therethrough, said second arraycomprising a second plurality of staggered, elongated openings, whereinsaid second plurality of said second array openings are elongated in adirection from the top to the bottom of the back member, wherein saidfirst plurality of openings have a greater elongation on average thansaid second plurality of openings.
 57. The invention of claim 56 whereinsaid lower region comprises a third array of openings formedtherethrough, said third array comprising a third plurality ofstaggered, elongated openings, wherein said first plurality of openingshave a greater elongation on average than said third plurality ofopenings.
 58. The invention of claim 56 wherein back member has a firstthickness at a center portion of said lumbar region and a secondthickness at a peripheral side portion of said lumbar region, whereinsaid second thickness is greater than said first thickness.
 59. Theinvention of claim 56 wherein said back member comprises a peripheralportion defining a periphery of said back member, wherein saidperipheral portion comprises a plurality of openings formedtherethrough.
 60. The invention of claim 56 wherein said back member isbowed at said lumbar region.
 61. The invention of claim 56 wherein saidback member is made of polypropylene.
 62. The invention of claim 56wherein said top of said back member comprises a curved portion defininga convex forward body support surface along a peripheral portion of saidback member.
 63. The invention of claim 56 wherein said frame member issecured to said back member at a pair of spaced apart upper locationsand a lower location.
 64. The invention of claim 63 wherein said upperlocations are spaced from said top of said back member.
 65. Theinvention of claim 56 further comprising a lumbar support memberconnected to said frame and engaging a rear surface of said back memberin said lumbar region thereof.
 66. The invention of claim 65 whereinsaid lumbar support member comprises a laterally extending lumbar frameconnected to said frame member and a flexible belt member mounted onsaid lumbar frame and engaging said rear surface of said back member.67. The invention of claim 66 wherein said lumbar frame is bow shaped.68. A backrest for a seating structure, the backrest comprising: a framemember comprising an upper support member and a lower support memberspaced from said upper support member, said upper support member havingopposite shoulder portions; a fabric member having a front,body-supporting surface and a rear surface and comprising at least onepocket received on said opposite shoulder portions, and wherein saidfabric member is connected to said lower support member and extends intension between said upper and lower support members, and wherein saidfabric member comprises a central thoracic region that is free ofcontact on said rear surface thereof.
 69. The invention of claim 68wherein said frame member comprises a central spine portion and whereinsaid opposite shoulder portion extend outwardly and forwardly therefrom.70. The invention of claim 68 wherein said frame member furthercomprises a lumbar support disposed between said upper and lowerportions, wherein said lumbar support engages said rear surface of saidfabric.
 71. The invention of claim 70 wherein said lumbar supportcomprises a frame member having opposite ends and a belt memberextending between said opposite ends, and wherein said belt memberengages said rear surface of said fabric.
 72. A backrest for a seatstructure, the backrest comprising: a back member having a top, a bottomand opposite sides, said back member comprising a plurality of openingsformed therein, wherein said plurality of openings transition from anobround shape to a peanut-shape to a substantially circular shapebetween first and second locations between said top and bottom, whereinsaid second location is spaced above said first location.
 73. Theinvention of claim 72 wherein said plurality of openings furthertransition from said obround shape to said peanut-shape to saidsubstantially circular shape between said first location and a thirdlocation between said top and bottom, wherein said third location isspaced below said first location.
 74. A seating structure comprising: asupport housing comprising a wall and a pivot tube extendingtherethrough; an insert member having an insert portion, wherein saidinsert member is moveably between a first position, wherein said insertmember is not inserted into said tube, and a second position, whereinsaid insert member is inserted into said pivot tube with an interferencefit, and wherein said pivot tube is expanded from a first shape to asecond shape as said insert member is moved from said first position tosaid second position, and wherein said pivot tube is fixedly secured tosaid wall when said pivot tube is expanded to said second shape; and aseating component pivotally mounted on said insert member.
 75. A methodfor assembling a seating structure comprising: inserting a pivot tubethrough an opening formed in a support housing; pivotally mounting aseating component on an insert member, wherein said insert membercomprises an insert portion; and pressing said insert portion into saidpivot tube with an interference fit and thereby expanding said pivottube at said opening and fixedly securing said pivot tube to saidsupport housing.
 76. The invention of claim 75 wherein said seatingcomponent comprises a backrest.
 77. A method for assembling a seatingstructure: providing a pivot member extending from one of a seatingcomponent and a support, wherein said pivot member has an outer arcedpivot surface formed at least around a portion of a periphery of saidpivot member, wherein said outer pivot surface is defined by a radiusand a first diameter and a first center defining a first pivot axis, anda key surface, at least a portion of said key surface formed at a firstdistance from said center, wherein said first distance is less than saidradius; providing a bearing member on the other of said seatingcomponent and said support, said bearing member having an openingdefined by an inner arced pivot surface having a second radius, a seconddiameter, a second center defining a second pivot axis and a mouthhaving a width, wherein said width is less than said second diameter,wherein said width is less than said first diameter and wherein saidwidth is greater than or equal to a sum of said first distance and saidradius; orienting said pivot member relative to said bearing member suchthat said at least said portion of said key surface defined by saidfirst distance is substantially perpendicular to said mouth; andinserting said pivot member through said mouth and into said openingalong a path substantially perpendicular to said first and second pivotaxes until said first and second pivot axes are substantially coaxial;and rotating one of said seating component and said support such thatsaid at least said portion of said key surface defined by said firstdistance is not substantially perpendicular to said mouth.
 78. Theinvention of claim 77 wherein said key surface defines a chord of saidouter arced pivot surface.
 79. A chair comprising: a housing comprisinga track having a curvilinear support surface formed within a verticalplane; a back support pivotally connected to said housing about a firsthorizontal axis; and a seat support pivotally connected to said backsupport about a second horizontal axis and moveably supported on saidsupport surface of said track.
 80. The invention of claim 79 whereinsaid seat support comprises a rotatable wheel, wherein said wheelengages said track.
 81. The invention of claim 80 wherein said housingcomprises a pair of said curvilinear tracks, and wherein said seatsupport comprises a pair of wheels engaging said tracks respectively.82. The invention of claim 79 wherein at least a portion of said supportsurface of said track has a convex curvature.
 83. A chair comprising: ahousing; a seat support supported by said housing; at least one leafspring comprising a first end supported by said housing and a second endbiasing said seat support in an upward direction, wherein said at leastone leaf spring flexes within a substantially vertical first plane; anda fulcrum member moveably supported by said housing and having a supportsurface engaging said at least one leaf spring between said first andsecond ends, wherein said support surface is not symmetrical about anylaterally extending second vertical plane oriented substantiallyperpendicular to said first plane.
 84. The invention of claim 83 furthercomprising a back support pivotally connected to said seat support at afirst pivot axis, wherein said at least one leaf spring biases said seatsupport and said back support in said upward direction.
 85. A chaircomprising: a housing; a back support pivotally connected to saidhousing about a first horizontal axis; a seat support pivotallyconnected to said back support about a second horizontal axis; at leastone leaf spring comprising a first end supported by said housing and asecond end biasing said back support and said seat support in an upwarddirection; and a fulcrum member moveably supported by said housing andhaving a curvilinear support surface engaging said at least one leafspring between said first and second ends, wherein a tangent of anypoint along said support surface slopes rearwardly and downwardly. 86.The invention of claim 85 wherein at least a portion of said supportsurface forms an arc.
 87. The invention of claim 86 wherein said arc hasa radius of between about 5 inches and 7 inches.
 88. A chair comprising:a housing; a seat support supported by said housing; at least one leafspring comprising a first end supported by said housing and a second endbiasing said seat support in an upward direction; a fulcrum membermoveably supported by said housing and having a support surface engagingsaid at least one leaf spring between said first and second ends; and alinkage assembly comprising a first and second link pivotally connectedto said housing about a first pivot axis, said first link pivotally andslidably connected to said fulcrum at a second pivot axis spaced fromsaid first pivot axis and said second link pivotally and slidablyconnected to said fulcrum at a third pivot axis spaced from said firstand second pivot axes.
 89. The invention of claim 88 wherein one of saidfulcrum and said first link has a first track, wherein one of saidfulcrum and said second link has a second track, and wherein the otherof said fulcrum and said first and said links has a first and secondguide member disposed in said first and second tracks respectively anddefining said second and third pivot axes respectively.
 90. Theinvention of claim 89 wherein said fulcrum is moveable in opposite firstand second directions, and further comprising an actuator comprising anactuator member moveable in opposite third and fourth directionssubstantially perpendicular to said first and second directions, whereinsaid actuator member pivotally and slideably connected to said first andsecond links at fourth and fifth pivot axes respectively, wherein saidfourth pivot axis is spaced from said first and second pivot axis andwherein said fifth pivot axis is spaced from said first and third pivotaxis.
 91. The invention of claim 90 wherein said actuator furthercomprises a screw threadably engaging said actuator member, wherein saidscrew is rotatable in a first and second rotational direction, whereinrotation of said screw in said first direction moves said actuatormember in said third direction and wherein said rotation of said screwin said second direction causes said actuator member to move in saidfourth direction.
 92. The invention of claim 90 wherein one of saidactuator member and said first link has a third track, wherein one ofsaid actuator member and said second link has a fourth track, andwherein the other of said actuator fulcrum and said first and said linkshas a third and fourth guide member disposed in said third and fourthtracks respectively and defining said fourth and fifth pivot axesrespectively.
 93. The invention of claim 92 wherein said housingcomprises a first bracket having a fifth and sixth track, wherein saidfifth and sixth tracks are curved, wherein said first and second guidemembers are slidably disposed in said fifth and sixth tracksrespectively.
 94. The invention of claim 93 wherein said housing furthercomprises a second bracket having a seventh and eighth track, whereinsaid seventh and eighth tracks are curved, wherein said third and fourthguide members are slidably disposed in said seventh and eighth tracksrespectively.
 95. The invention of claim 94 wherein said fifth and sixthtracks have a radius substantially equal to the distance between thefirst and second pivot member and the first pivot axis respectively, andwherein said seventh and eighth tracks have a radius substantially equalto the distance between the third and fourth pivot member and the firstpivot axis respectively.
 96. A method for assembling a seating structurecomprising: providing an annular bushing having first and secondopposite ends and comprising a first annular flange extending radiallyoutward therefrom adjacent said first end thereof; disposing a pluralityof tilt control housing components on said bushing and abutting saidfirst flange with at least one of said plurality of components; anddeforming said second end of said bushing and thereby forming a secondannular flange extending radially outward from said bushing; andcapturing said plurality of tilt control housing components between saidfirst and second flanges.
 97. A seating structure comprising: a housing;a support member pivotally mounted to said housing; a tilt limitermember moveably mounted to one of said housing and said support member;a stop member connected to the other of said support member and saidhousing; and an actuator mechanism coupled to said one of said housingand said support member, said actuator mechanism comprising a springhaving a first and second arm, a drive link pivotally mounted to saidone of said housing and said support member about a first axis andengaging said first arm of said spring at a first location spaced fromsaid first axis, a follower link pivotally mounted to said one of saidhousing and said support member about a second axis spaced from saidfirst axis and engaging said second arm of said spring at a secondlocation spaced from said second axis, and said follower link pivotallycoupled to said tilt limiter member.
 98. The invention of claim 97wherein said actuator mechanism further comprises a coupling linkpivotally connected to said follower link at a third axis and pivotallyconnected to said tilt limiter at a fourth axis spaced from said thirdaxis.
 99. The invention of claim 97 wherein support member comprises abracket, and wherein said drive link and said follower link arepivotally mounted to said bracket, wherein said tilt limiter member ismoveably mounted to said support member, and wherein said stop member isconnected to said housing.
 100. The invention of claim 99 wherein saidstop member comprises a plurality of steps, wherein said tilt limitermember is moveable to a plurality of positions wherein said tilt limitermember selectively engages at least one of said plurality of steps whenin one of said plurality of positions.
 101. The invention of claim 97wherein said stop member has a downwardly facing stop surface and saidtilt limiter has an upwardly facing bearing surface engaging said stopsurface.
 102. The invention of claim 97 wherein said stop member has atleast one upwardly facing stop surface and said tilt limiter has adownwardly facing bearing surface engaging said at least one stopsurface.
 103. The invention of claim 97 wherein said drive linkcomprises a rack formed therealong, and an indexing member selectivelyand releasably engaged with said rack.
 104. The invention of claim 103wherein said indexing member comprises a cantilevered spring having afree end selectively and releasably engaged with said rack.
 105. Theinvention of claim 97 wherein said actuator mechanism comprises a driveshaft connected to said drive link, wherein said drive shaft isrotatably mounted to said one of said housing and said support memberabout said first axis, and further comprising a grippable member mountedto an end of said drive shaft.
 106. The invention of claim 97 whereinsaid tilt limiter member comprises a first and second tilt limitermember moveably mounted to one of said housing and said support member,wherein said stop member comprises a first and second stop memberconnected to the other of said support member and said housing, andwherein said actuator mechanism comprises first and second springs eachhaving a first and second arm, spaced apart first and second drive linkseach pivotally mounted to said one of said housing and said supportmember about said first axis and engaging said first arm of said firstand second springs respectively at first locations on each of said firstand second drive links spaced from said first axis, first and secondfollower links, wherein said first follower link is pivotally mounted tosaid one of said housing and said support member about said second axisand wherein said second follower link is pivotally mounted to one ofsaid housing and said support member about a third axis spaced from saidfirst axis, wherein said first and second follower links engage saidsecond arms of said first and second springs respectively at secondlocations on each of said first and second follower links spaced fromsaid second axis, and said first and second follower links pivotallycoupled to said first and second tilt limiter members respectively. 107.The invention of claim 106 wherein said actuator mechanism comprises afirst and second drive shaft connected to said first and second drivelinks respectively, wherein said first and second drive shafts arecoaxially and rotatably mounted to said one of said housing and saidsupport member about said first axis.
 108. The invention of claim 106wherein said second and third axes are coaxial.
 109. A kit forassembling a seating structure comprising: a tilt housing having aplurality of connector arrangements comprising at least a first andsecond connector arrangement; a first seating arrangement having a firstmounting arrangement configured to be connected to said first connectorarrangement; and a second seating arrangement having a second mountingarrangement configured to be connected to said second connectorarrangement.
 110. The invention of claim 109 wherein said first seatingarrangement comprises a seat pivotally connected to a back at a firstpivot axis, wherein said first mounting arrangement comprises a firstpivot structure formed on said back, and wherein said first connectorarrangement comprises a second pivot structure configured for pivotalconnection to said first pivot structure.
 111. The invention of claim110 wherein said first mounting arrangement further comprises a thirdpivot structure formed on said seat, and wherein said first connectorarrangement comprises a fourth pivot structure configured for pivotalconnection to said third pivot structure.
 112. The invention of claim111 wherein said fourth pivot structure comprises a guide configured totranslatably support said third pivot structure.
 113. The invention ofclaim 112 wherein said guide comprises a fender connected to said tilthousing.
 114. The invention of claim 109 wherein said first seatingarrangement comprises a seat connected to a back, wherein said firstmounting arrangement comprises a linkage assembly pivotally connected toat least one of said seat and back and defining a first plurality ofpivot structures, and wherein said first connector arrangement comprisesa second plurality of pivot structures, wherein said first plurality ofpivot structures is configured for pivotal connection to said secondplurality of pivot structures.
 115. The invention of claim 109 whereinsaid first connector arrangement and said first mounting arrangementform a three-bar slide configuration, and wherein said second connectorarrangement and said second mounting arrangement form a four-barconfiguration.
 116. A method of assembling a seating structurecomprising: providing a tilt housing having a plurality of connectorarrangements comprising at least a first and second connectorarrangement; selecting one of a first and second seating arrangements,wherein said first seating arrangement comprises a first mountingarrangement configured to be connected to said first connectorarrangement, and wherein said second seating arrangement comprises asecond mounting arrangement configured to be connected to said secondconnector arrangement; and connecting said selected one of said firstand second seating arrangements to said tilt housing.
 117. The inventionof claim 116 wherein said selecting said one of said first and secondseating arrangements comprises selecting said first seating arrangement,wherein said first seating arrangement comprises a seat pivotallyconnected to a back at a first pivot axis, wherein said first mountingarrangement comprises a first pivot structure formed on said back, andwherein said first connector arrangement comprises a second pivotstructure formed on said tilt housing, and wherein said connecting saidselected one of said first and second seating arrangements to said tilthousing comprises pivotally connecting said first pivot structure tosaid second pivot structure.
 118. The invention of claim 117 whereinsaid first mounting arrangement further comprises a third pivotstructure formed on said seat, and wherein said first connectorarrangement comprises a fourth pivot structure, and wherein saidconnecting said selected one of said first and second seatingarrangements to said tilt housing further comprises pivotally connectingsaid third pivot structure to said fourth pivot structure.
 119. Theinvention of claim 118 wherein said fourth pivot structure furthercomprises a guide configured to translatably support said third pivotstructure.
 120. The invention of claim 119 wherein said guide comprisesa fender connected to said tilt housing.
 121. The invention of claim 116wherein said selecting said one of said first and second seatingarrangements comprises selecting said first seating arrangement, whereinsaid first seating arrangement comprises a seat connected to a back,wherein said first mounting arrangement comprises a linkage assemblypivotally connected to at least one of said seat and back and defining afirst plurality of pivot structures, and wherein said first connectorarrangement comprises a second plurality of pivot structures, whereinsaid connecting said selected one of said first and second seatingarrangements to said tilt housing comprises pivotally connecting saidfirst plurality of pivot structures to said second plurality of pivotstructures.
 122. The invention of claim 116 wherein said first connectorarrangement and said first mounting arrangement form a three-bar slideconfiguration, and wherein said second connector arrangement and saidsecond mounting arrangement form a four-bar configuration.
 123. Aseating structure comprising: a tilt housing having a support surface; aback support pivotally connected to said tilt housing about a firstpivot axis; and a tilt limiter pivotally connected to said tilt housingabout a second pivot axis, said tilt limiter having a bearing surfacespaced from said second pivot axis, said bearing surface supported bysaid support surface of said tilt housing.
 124. A seating structurecomprising: a tilt housing; a back support pivotally connected to saidtilt housing about a first pivot axis, wherein said back support ispivotable about said first pivot axis in a first and second direction,said back support having a forwarding facing edge and a top and bottomsurface formed along said edge; a forward tilt limiter pivotallyconnected to said tilt housing about a second pivot axis, said forwardtilt limiter pivotable between at least a first and second forward tiltposition, wherein said forward tilt limiter engages said top surface ofsaid back support when in at least one of said first and second forwardtilt positions and thereby limits the pivoting of said back support insaid first direction; a rear tilt limiter pivotally connected to saidtilt housing about a third pivot axis, said rear tilt limiter pivotablebetween at least a first and second rear tilt position, wherein saidrear tilt limiter engages said bottom surface of said back support whenin at least one of said first and second rear tilt positions and therebylimits the pivoting of said back support in said second direction. 125.A seating structure comprising: a tilt housing; a seating structurepivotally connected to said tilt housing; a biasing member applying abiasing force to said seating structure as said seating structure ispivoted relative to said tilt housing; an adjustment mechanism operablyconnected to said biasing member, wherein said adjustment mechanism isoperable to adjust said biasing force applied by said biasing member,said adjustment mechanism comprising a gear housing removably disposedin said tilt housing and rotatably connected to said tilt housing aboutan axis, said gear housing comprising first and second locator portionsabutting said tilt housing, wherein said first locator portion preventssaid gear housing from moving relative to said tilt housing in a firstdirection, and wherein said second locator portion prevents said gearhousing from rotating relative to said tilt housing about said axis.126. The invention of claim 125 wherein said first locator portionfurther prevents said gear housing from moving relative to said tilthousing in a second direction substantially perpendicular to said firstdirection.
 127. The invention of claim 126 wherein said biasing memberapplies a force to said gear housing and thereby prevents said gearhousing from moving in a third direction substantially perpendicular tosaid first and second directions.
 128. The invention of claim 127wherein said adjustment mechanism comprises a drive shaft extending fromsaid gear housing, wherein said drive shaft is coupled to a fulcrummember, wherein said biasing member comprises a leaf spring engagingsaid fulcrum member.
 129. The invention of claim 125 wherein saidadjustment mechanism comprises first and second meshing gears disposedin said gear housing.
 130. A method of assembling a seating structurecomprising: providing a tilt housing and a seating structure pivotallyconnected to said tilt housing; rotatably connecting a gear housing tosaid tilt housing about an axis; abutting a first locator portion ofsaid gear housing against said tilt housing so as to prevent said gearhousing from moving relative to said housing in a first direction; andabutting a second locator portion of said gear housing against said tilthousing so as to prevent said gear housing from rotating about saidaxis.
 131. The invention of claim 130 wherein said first locator portionfurther prevents said gear housing from moving relative to said tilthousing in a second direction substantially perpendicular to said firstdirection.
 132. The invention of claim 130 further comprising installinga biasing member and thereby applying a biasing force to said seatingstructure as said seating structure is pivoted relative to said tilthousing, and applying a force with said biasing member to said gearhousing so as to thereby prevent said gear housing from moving in athird direction substantially perpendicular to said first and seconddirections.
 133. The invention of claim 132 further comprising providinga drive shaft extending from said gear box, wherein said drive shaft iscoupled to a fulcrum member, wherein said biasing member comprises aleaf spring engaging said fulcrum member, and wherein said applying saidforce with said biasing member to said gear housing comprises applyingsaid force with said biasing member to said gear housing by way of saidfulcrum and said drive shaft.
 134. A support member for a seatingstructure component, support member comprising: a first support memberhaving a first plurality of spaced apart fins; a second support memberhaving a second plurality of spaced apart fins; wherein said firstsupport member is secured to said second support member with said firstplurality of fins nested between said second plurality of fins.
 135. Theinvention of claim 134 further comprising a back member connected to atleast one of said first and second support members.
 136. The inventionof claim 134 further comprising a back support member moveably coupledto at least one of said first and second support members.
 137. Theinvention of claim 136 wherein said first and second support membersform a gap therebetween, wherein said back support member comprises aengaging member disposed through said gap.
 138. The invention of claim137 wherein said back support member comprises a lumbar support.
 139. Aseating structure comprising: a base; a seat supported by said base andmoveable between a normal tilt position and a forward tilt position; abackrest supported by said base and moveable between a normal positionand at least one rear tilt position; a forward tilt limiter coupled toat least one of said seat and backrest to limit the movement of the seatbetween the normal and forward tilt positions, said forward tilt limitermoveable between a normal setting and a forward tilt setting; a reartilt limiter coupled to at least one of the seat and backrest to limitthe movement of the backrest between the normal and the at least onerear tilt position, said rear tilt limiter moveable between a normalsetting and at least one rear tilt setting; a forward tilt actuatorcoupled to the forward tilt mechanism, wherein said forward tiltactuator is oriented in generally the same orientation as the seat, andwherein the position of the forward tilt actuator is indicative of thesetting of the forward tilt limiter; and a rear tilt actuator coupled tothe rear tilt mechanism, wherein said rear tilt actuator is oriented ingenerally the same orientation as the backrest, wherein the position ofthe rear tilt actuator is indicative of the setting of the rear tiltlimiter, and wherein said rear tilt actuator is positioned adjacent saidforward tilt actuator in generally the same relationship as the seat andbackrest.
 140. The invention of claim 139 wherein said rear tiltactuator has generally the same shape as the backrest.
 141. Theinvention of claim 139 wherein said forward tilt actuator has generallythe same shape as the seat.
 142. A control device for an adjustableseating structure, the control device comprising: a first adjustmentcontrol positioned in an orientation approximating a seating member,said first adjustment control moveable about a horizontal axis; a secondadjustment control positioned adjacent the seat adjustment control in anorientation approximating a backrest member, said second adjustmentcontrol moveable about said horizontal axis, wherein said firstadjustment control and said second adjustment control in combinationgenerally resemble a seating structure.
 143. The invention of claim 142wherein said second adjustment control is generally shaped like thebackrest member.
 144. The invention of claim 142 wherein said firstadjustment control is coupled to a forward tilt limiter, and whereinsaid second adjustment control is coupled to a rear tilt limiter.
 145. Akit for assembling a seating structure comprising: a back member; a backsupport member; a first support configuration adapted to be coupled tosaid back support member and adapted to support said back member; and asecond support configuration adapted to be coupled to said back supportmember and adapted to support said back member, wherein said secondsupport configuration provides different support to said back memberwhen coupled to said back support member than said first supportconfiguration.
 146. The invention of claim 145 wherein said first andsecond support configurations are each adapted to be adjustable coupledto said back support member.
 147. The invention of claim 146 whereinsaid back support member comprises a spine member, and wherein saidfirst and second support configurations are adapted to be slidablymounted on said spine member.
 148. A method of assembling a seatingstructure comprising: providing a back member, a back support member, afirst support configuration and a second support configuration, whereinsaid second support configuration is different than said first supportconfiguration; selecting one of said first and second supportconfigurations; coupling said selected one of said first and secondsupport configurations to said back support member; and supporting saidback member with said selected one of said first and second supportconfigurations.
 149. The invention of claim 148 wherein said couplingsaid selected one of said first and second support configurations tosaid back support member comprises adjustably coupling said selected oneof said first and second support configurations to said back supportmember.
 150. The invention of claim 149 wherein said back support membercomprises a spine member, and wherein said adjustably coupling saidselected one of said first and second support configurations to saidback support member comprises slidably mounting said selected one ofsaid first and second support configurations on said spine member.